{"id":3993,"date":"2026-05-21T04:56:43","date_gmt":"2026-05-21T03:56:43","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/identifying-compounds-from-mass-spectra\/"},"modified":"2026-05-26T11:07:07","modified_gmt":"2026-05-26T10:07:07","slug":"identifying-compounds-from-mass-spectra","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/identifying-compounds-from-mass-spectra\/","title":{"rendered":"Identifying Compounds from Mass Spectra"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-identifying-compounds-mass-spectra-page\">\n  <style>\n    .ols-revision-page {\n      --navy: #1C244B;\n      --blue: #2563eb;\n      --soft-blue: #eef4ff;\n      --soft-red: #fff7f7;\n      --soft-purple: #f7f0ff;\n      --soft-green: #f0f7f1;\n      --soft-orange: #fff7ed;\n      --gold: #c9973a;\n      --grey-text: #667085;\n      --body-text: #1f2937;\n      --border: rgba(28, 36, 75, 0.14);\n      --shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      --inner-shadow: 0 10px 26px rgba(28, 36, 75, 0.08);\n      font-family: Poppins, Arial, sans-serif;\n      color: var(--navy);\n      background: #ffffff;\n    }\n\n    .ols-revision-page * { box-sizing: border-box; }\n\n    \n\n    \n\n    \n\n    \n\n    \n\n    \n\n    \n\n    \n\n    \n\n    \n\n    \n\n    \n\n    \n\n    \n\n    \n\n    \n\n    \n    \n\n    .ols-main {\n      min-width: 0;\n      max-width: 970px;\n    }\n\n    .ols-breadcrumbs {\n      display: flex;\n      flex-wrap: wrap;\n      gap: 8px;\n      margin: 10px 0 22px;\n      font-size: 15px;\n      color: var(--grey-text);\n    }\n\n    .ols-breadcrumbs a,\n    .ols-breadcrumbs span {\n      color: var(--grey-text);\n      text-decoration: none;\n      font-weight: 600;\n    }\n\n    .ols-breadcrumbs a:hover {\n      color: var(--blue);\n      text-decoration: underline;\n      text-underline-offset: 3px;\n    }\n\n    .ols-title-card,\n    .ols-note-card,\n    .ols-h5p-card,\n    .ols-related-card,\n    .ols-faq-card,\n    .ols-quicksnap-card,\n    .ols-attribution-card {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 28px;\n      box-shadow: var(--shadow);\n      padding: 34px;\n      margin-bottom: 24px;\n      overflow: hidden;\n    }\n\n    .ols-title-card { background: linear-gradient(135deg, #ffffff 0%, #f8fbff 100%); }\n\n    .ols-title-card h1 {\n      margin: 0 0 18px;\n      font-size: clamp(36px, 5vw, 58px);\n      line-height: 1.08;\n      font-weight: 800;\n      letter-spacing: -0.04em;\n      color: #111827;\n    }\n\n    .ols-page-intro {\n      font-size: 19px;\n      line-height: 1.7;\n      font-weight: 300;\n      color: var(--body-text);\n      margin: 0 0 22px;\n    }\n\n    .ols-badges {\n      display: flex;\n      flex-wrap: wrap;\n      gap: 12px;\n      margin-bottom: 22px;\n    }\n\n    .ols-badge {\n      display: inline-flex;\n      align-items: center;\n      padding: 9px 14px;\n      border-radius: 999px;\n      background: #ffffff;\n      border: 1px solid var(--border);\n      font-size: 15px;\n      font-weight: 600;\n      color: var(--navy);\n    }\n\n    .ols-author {\n      display: flex;\n      align-items: center;\n      gap: 20px;\n      padding: 28px;\n      border-radius: 28px;\n      background: linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n      border: 1px solid rgba(28,36,75,0.12);\n      box-shadow: 0 18px 45px rgba(28,36,75,0.10);\n      margin-top: 22px;\n    }\n\n    .ols-author-avatar-img {\n      width: 92px;\n      height: 92px;\n      border-radius: 50%;\n      object-fit: cover;\n      object-position: center;\n      flex-shrink: 0;\n      border: 4px solid #ffffff;\n      box-shadow: 0 14px 32px rgba(28,36,75,0.18), 0 0 0 1px rgba(28,36,75,0.10);\n    }\n\n    .ols-author-title {\n      margin: 0 0 4px;\n      font-size: clamp(24px,3vw,34px);\n      line-height: 1.15;\n      font-weight: 700;\n      color: var(--navy);\n      letter-spacing: -0.03em;\n    }\n\n    .ols-author-description {\n      margin: 0;\n      font-size: 17px;\n      line-height: 1.7;\n      font-weight: 300;\n      color: var(--grey-text);\n    }\n\n    .ols-linkedin-pill {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      gap: 10px;\n      margin-top: 16px;\n      padding: 11px 18px;\n      border-radius: 999px;\n      background: linear-gradient(135deg,#0A66C2,#004182);\n      color: #ffffff;\n      text-decoration: none;\n      font-size: 14px;\n      line-height: 1;\n      font-weight: 700;\n      box-shadow: 0 10px 22px rgba(10,102,194,0.24);\n      transition: transform 0.22s ease, box-shadow 0.22s ease;\n    }\n\n    .ols-linkedin-pill:hover {\n      transform: translateY(-3px) scale(1.03);\n      box-shadow: 0 16px 34px rgba(10,102,194,0.34), 0 0 0 6px rgba(10,102,194,0.10);\n      color: #ffffff;\n    }\n\n    .ols-linkedin-icon {\n      width: 18px;\n      height: 18px;\n      display: block;\n      flex-shrink: 0;\n    }\n\n    .ols-note-card.soft { background: linear-gradient(135deg, #ffffff 0%, var(--soft-red) 100%); }\n    .ols-note-card.purple { background: linear-gradient(135deg, #ffffff 0%, var(--soft-purple) 100%); }\n    .ols-note-card.orange { background: linear-gradient(135deg, #ffffff 0%, var(--soft-orange) 100%); }\n\n    .ols-note-title {\n      display: flex;\n      align-items: center;\n      gap: 14px;\n      margin-bottom: 20px;\n    }\n\n    .ols-note-icon {\n      width: 52px;\n      height: 52px;\n      border-radius: 16px;\n      background: var(--navy);\n      color: #ffffff;\n      display: grid;\n      place-items: center;\n      font-size: 24px;\n      font-weight: 800;\n      flex-shrink: 0;\n    }\n\n    .ols-note-title h2,\n    .ols-h5p-card h2,\n    .ols-related-card h2,\n    .ols-faq-card h2,\n    .ols-quicksnap-card h2 {\n      margin: 0;\n      font-size: clamp(28px, 3.5vw, 42px);\n      line-height: 1.15;\n      font-weight: 800;\n      color: #111827;\n      letter-spacing: -0.03em;\n    }\n\n    .ols-h5p-card h2,\n    .ols-related-card h2,\n    .ols-faq-card h2,\n    .ols-quicksnap-card h2 { margin-bottom: 14px; }\n\n    .ols-note-card p,\n    .ols-note-card li {\n      font-size: clamp(15px, 1.25vw, 17px);\n      line-height: 1.65;\n      font-weight: 300;\n      color: var(--body-text);\n    }\n\n    .ols-h5p-card p,\n    .ols-related-card p,\n    .ols-faq-card p,\n    .ols-quicksnap-card p {\n      font-size: clamp(15px, 1.3vw, 18px);\n      line-height: 1.65;\n      font-weight: 300;\n      color: var(--body-text);\n    }\n\n    .ols-note-card strong,\n    .ols-h5p-card strong,\n    .ols-related-card strong,\n    .ols-faq-card strong,\n    .ols-quicksnap-card strong { font-weight: 700; color: var(--navy); }\n\n    .ols-note-card ul,\n    .ols-note-card ol { margin: 0; padding-left: 22px; }\n\n    .ols-key-box {\n      margin-top: 20px;\n      background: var(--soft-green);\n      border: 1px solid rgba(63, 143, 70, 0.25);\n      border-radius: 20px;\n      padding: 18px 20px;\n    }\n\n    .ols-key-box p {\n      margin: 0;\n      font-weight: 400;\n      color: var(--navy);\n    }\n\n    .ols-definition-box {\n      margin-top: 20px;\n      background: linear-gradient(135deg, #ffffff, var(--soft-purple));\n      border: 2px dashed rgba(122, 62, 157, 0.35);\n      border-radius: 24px;\n      padding: 22px;\n    }\n\n    .ols-definition-box p { margin: 0; }\n\n    .ols-formula-box {\n      margin: 22px 0 4px;\n      padding: 22px;\n      border-radius: 22px;\n      border: 1px solid rgba(37, 99, 235, 0.18);\n      background: linear-gradient(135deg, #ffffff, var(--soft-blue));\n      box-shadow: var(--inner-shadow);\n      text-align: center;\n    }\n\n    .ols-formula-box p {\n      margin: 0;\n      font-size: clamp(20px, 2.6vw, 32px);\n      line-height: 1.45;\n      font-weight: 800;\n      color: var(--navy);\n      overflow-wrap: anywhere;\n    }\n\n    .ols-formula-box small {\n      display: block;\n      margin-top: 10px;\n      font-size: 14px;\n      line-height: 1.55;\n      color: var(--grey-text);\n      font-weight: 400;\n    }\n\n    .ols-rule-list,\n    .ols-worked-grid {\n      display: grid;\n      gap: 14px;\n      margin-top: 18px;\n    }\n\n    .ols-rule-item,\n    .ols-worked-step {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-left: 5px solid var(--blue);\n      border-radius: 18px;\n      padding: 18px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-rule-item h3,\n    .ols-worked-step h3 {\n      margin: 0 0 8px;\n      font-size: 20px;\n      line-height: 1.25;\n      color: var(--navy);\n    }\n\n    .ols-rule-item p,\n    .ols-worked-step p {\n      margin: 0;\n      font-size: 15px;\n      line-height: 1.6;\n    }\n\n    .ols-figure-card {\n      margin: 26px 0 4px;\n      border: 1px solid var(--border);\n      border-radius: 26px;\n      overflow: hidden;\n      background: #ffffff;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-figure-image {\n      width: 100%;\n      min-height: 260px;\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      background: #ffffff;\n      padding: 20px;\n    }\n\n    .ols-figure-image img {\n      max-width: 100%;\n      height: auto;\n      display: block;\n    }\n\n    .ols-figure-caption {\n      padding: 20px 24px 22px;\n      background: linear-gradient(135deg, #ffffff, #f8fbff);\n      border-top: 1px solid var(--border);\n    }\n\n    .ols-figure-caption p {\n      margin: 0;\n      color: #5f6b85;\n      font-size: clamp(15px, 1.3vw, 17px);\n      line-height: 1.6;\n      font-weight: 300;\n      font-style: italic;\n    }\n\n    .ols-table-wrap {\n      overflow: hidden;\n      border-radius: 22px;\n      border: 1px solid var(--border);\n      background: #ffffff;\n      margin-top: 18px;\n    }\n\n    .ols-table {\n      width: 100%;\n      border-collapse: collapse;\n      table-layout: fixed;\n    }\n\n    .ols-table th {\n      background: var(--navy);\n      color: #ffffff;\n      padding: 16px;\n      text-align: left;\n      font-size: clamp(14px, 1.2vw, 17px);\n      font-weight: 600;\n      overflow-wrap: anywhere;\n    }\n\n    .ols-table td {\n      padding: 16px;\n      border-bottom: 1px solid var(--border);\n      font-size: clamp(14px, 1.15vw, 16px);\n      line-height: 1.45;\n      color: var(--body-text);\n      vertical-align: top;\n      overflow-wrap: anywhere;\n    }\n\n    .ols-table tr:last-child td { border-bottom: none; }\n\n    .ols-h5p-card { background: linear-gradient(135deg, #ffffff 0%, #f7f0ff 100%); }\n\n    .ols-h5p-grid {\n      display: grid;\n      grid-template-columns: 1fr;\n      gap: 16px;\n      margin-top: 22px;\n    }\n\n    .ols-h5p-frame {\n      padding: 18px;\n      border-radius: 24px;\n      background: #ffffff;\n      border: 1px solid var(--border);\n      box-shadow: inset 0 0 0 1px rgba(28, 36, 75, 0.03);\n    }\n\n    .ols-quicksnap-card {\n      background:\n        radial-gradient(circle at top left, rgba(201,151,58,0.15), transparent 30%),\n        linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n    }\n\n    .ols-snap-list {\n      display: grid;\n      gap: 12px;\n      margin-top: 18px;\n    }\n\n    .ols-snap-item {\n      display: grid;\n      grid-template-columns: 42px 1fr;\n      gap: 12px;\n      align-items: start;\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 16px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-snap-number {\n      width: 42px;\n      height: 42px;\n      border-radius: 14px;\n      background: var(--navy);\n      color: #ffffff;\n      display: grid;\n      place-items: center;\n      font-weight: 800;\n    }\n\n    .ols-snap-item p {\n      margin: 0;\n      font-size: 16px;\n      line-height: 1.6;\n    }\n\n    .ols-course-cta {\n      width: 100%;\n      margin: 30px 0 24px;\n      font-family: Poppins, Arial, sans-serif;\n    }\n\n    .ols-course-cta-card {\n      overflow: hidden;\n      border-radius: 30px;\n      border: 1px solid var(--border);\n      background:\n        radial-gradient(circle at top left, rgba(37, 99, 235, 0.16), transparent 34%),\n        linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n      box-shadow: var(--shadow);\n      padding: 30px;\n    }\n\n    .ols-course-cta-top {\n      display: grid;\n      grid-template-columns: minmax(250px, 0.86fr) minmax(0, 1.14fr);\n      gap: 28px;\n      align-items: center;\n      margin-bottom: 24px;\n    }\n\n    .ols-course-cta-image-link,\n    .ols-course-button { text-decoration: none; }\n\n    .ols-course-cta-image {\n      width: 100%;\n      border-radius: 24px;\n      overflow: hidden;\n      border: 1px solid var(--border);\n      background: #ffffff;\n      box-shadow: var(--inner-shadow);\n      transition: transform 0.35s ease, box-shadow 0.35s ease;\n    }\n\n    .ols-course-cta-image img {\n      width: 100%;\n      height: auto;\n      display: block;\n      transition: transform 0.45s ease;\n    }\n\n    .ols-course-cta-image-link:hover .ols-course-cta-image {\n      transform: translateY(-8px) scale(1.015);\n      box-shadow: 0 26px 60px rgba(28, 36, 75, 0.18), 0 0 0 1px rgba(37, 99, 235, 0.12);\n    }\n\n    .ols-course-cta-image-link:hover .ols-course-cta-image img { transform: scale(1.03); }\n\n    .ols-course-cta-kicker {\n      display: inline-flex;\n      align-items: center;\n      padding: 8px 14px;\n      border-radius: 999px;\n      background: #ffffff;\n      border: 1px solid rgba(37, 99, 235, 0.18);\n      color: var(--blue);\n      font-size: 14px;\n      line-height: 1.2;\n      font-weight: 700;\n      box-shadow: var(--inner-shadow);\n      margin-bottom: 16px;\n    }\n\n    .ols-course-cta h2 {\n      margin: 0 0 14px;\n      font-size: clamp(28px, 3.5vw, 42px);\n      line-height: 1.15;\n      font-weight: 800;\n      letter-spacing: -0.03em;\n      color: #111827;\n    }\n\n    .ols-course-cta p {\n      margin: 0;\n      color: var(--body-text);\n      font-size: clamp(16px, 1.4vw, 18px);\n      line-height: 1.7;\n      font-weight: 300;\n    }\n\n    .ols-course-stats {\n      display: grid;\n      grid-template-columns: repeat(4, minmax(0, 1fr));\n      gap: 14px;\n      margin: 24px 0;\n    }\n\n    .ols-course-stat {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 16px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-course-stat span {\n      display: block;\n      margin-bottom: 6px;\n      color: var(--grey-text);\n      font-size: 13px;\n      line-height: 1.35;\n      font-weight: 700;\n    }\n\n    .ols-course-stat strong {\n      display: block;\n      color: var(--navy);\n      font-size: 18px;\n      line-height: 1.35;\n      font-weight: 800;\n    }\n\n    .ols-course-button {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      padding: 15px 28px;\n      border-radius: 999px;\n      background: var(--navy);\n      color: #ffffff;\n      font-size: 16px;\n      line-height: 1.2;\n      font-weight: 800;\n      box-shadow: 0 12px 26px rgba(28, 36, 75, 0.18);\n      transition: transform 0.2s ease, background 0.2s ease, box-shadow 0.2s ease;\n    }\n\n    .ols-course-button:hover {\n      transform: translateY(-2px);\n      background: var(--blue);\n      color: #ffffff;\n      box-shadow: 0 16px 32px rgba(37, 99, 235, 0.24);\n    }\n\n    .ols-faq-list {\n      display: grid;\n      gap: 14px;\n      margin-top: 18px;\n    }\n\n    .ols-faq-item {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 18px 20px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-faq-item h3 {\n      margin: 0 0 8px;\n      font-size: 20px;\n      line-height: 1.3;\n      color: var(--navy);\n    }\n\n    .ols-faq-item p {\n      margin: 0;\n      font-size: 16px;\n      line-height: 1.65;\n      color: var(--body-text);\n    }\n\n    .ols-related-grid {\n      display: grid;\n      grid-template-columns: repeat(3, minmax(0, 1fr));\n      gap: 16px;\n      margin-top: 18px;\n    }\n\n    .ols-related-item {\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 18px;\n      background: #ffffff;\n      color: var(--navy);\n      text-decoration: none;\n      font-weight: 600;\n      line-height: 1.5;\n      transition: transform 0.2s ease, box-shadow 0.2s ease;\n    }\n\n    .ols-related-item:hover {\n      transform: translateY(-2px);\n      box-shadow: 0 10px 22px rgba(28, 36, 75, 0.08);\n      color: var(--blue);\n    }\n\n    .ols-attribution-card {\n      background: linear-gradient(135deg, #ffffff, #f8fbff);\n    }\n\n    .ols-attribution-card p {\n      margin: 0;\n      font-size: 14px;\n      line-height: 1.65;\n      font-weight: 300;\n      color: #667085;\n    }\n\n    .ols-attribution-card strong {\n      font-weight: 700;\n      color: #1C244B;\n    }\n\n    @media (max-width: 1050px) {\n      \n      \n      \n      \n      .ols-main { max-width: none; }\n      .ols-related-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }\n      .ols-course-cta-top { grid-template-columns: 1fr; }\n      .ols-course-cta-image-link { max-width: 520px; margin: 0 auto; }\n      .ols-course-stats { grid-template-columns: repeat(2, minmax(0, 1fr)); }\n    }\n\n    @media (max-width: 760px) {\n      \n      .ols-title-card,\n      .ols-note-card,\n      .ols-h5p-card,\n      .ols-related-card,\n      .ols-faq-card,\n      .ols-quicksnap-card,\n      .ols-course-cta-card,\n      .ols-attribution-card {\n        padding: 24px 18px;\n        border-radius: 22px;\n      }\n\n      .ols-note-title { align-items: flex-start; }\n      \n      \n      .ols-figure-card { border-radius: 22px; }\n      .ols-figure-image { min-height: 210px; padding: 14px; }\n      .ols-figure-caption { padding: 18px; }\n\n      .ols-table-wrap {\n        border: none;\n        background: transparent;\n      }\n\n      .ols-table,\n      .ols-table thead,\n      .ols-table tbody,\n      .ols-table th,\n      .ols-table td,\n      .ols-table tr {\n        display: block;\n        width: 100%;\n      }\n\n      .ols-table thead { display: none; }\n\n      .ols-table tr {\n        margin-bottom: 14px;\n        border: 1px solid var(--border);\n        border-radius: 18px;\n        overflow: hidden;\n        background: #ffffff;\n        box-shadow: var(--inner-shadow);\n      }\n\n      .ols-table td {\n        border-bottom: 1px solid var(--border);\n        padding: 14px 16px;\n        overflow-wrap: anywhere;\n      }\n\n      .ols-table td:last-child { border-bottom: none; }\n\n      .ols-table td::before {\n        content: attr(data-label);\n        display: block;\n        margin-bottom: 6px;\n        font-size: 13px;\n        font-weight: 700;\n        color: var(--blue);\n      }\n\n      .ols-author {\n        align-items: flex-start;\n        padding: 22px 18px;\n        border-radius: 22px;\n      }\n\n      .ols-author-avatar-img {\n        width: 72px;\n        height: 72px;\n      }\n\n      .ols-author-title { font-size: 24px; }\n      .ols-author-description { font-size: 15px; }\n      .ols-snap-item { grid-template-columns: 1fr; }\n      .ols-course-button { width: 100%; }\n    }\n  <\/style>\n\n  <aside class=\"ols-sidebar\">\r\n  <div class=\"ols-sidebar-header\">\r\n    <h3>Revision Notes<\/h3>\r\n    <p>A Level Chemistry<\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Topic 2 Atomic Structure and The Periodic Table<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/atomic-structure\/\">Atomic Structure<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/\">Mass Spectrometry<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/the-mass-spectrometer\/\">The Mass Spectrometer<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/ram-calculations\/\">RAM Calculations<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/predicting-diatomic-mass-spectra\/\">Predicting Diatomic Mass Spectra<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/identifying-compounds-from-mass-spectra\/\">Identifying Compounds from Mass Spectra<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/quantum-model\/\">Quantum Model<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/\">Ionisation Energy<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/introduction-to-ionisation-energy\/\">Introduction to Ionisation Energy<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/successive-ionisation-energy\/\">Successive Ionisation Energy<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/trends-in-a-period\/\">Trends in a Period<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/trends-in-a-group\/\">Trends in a Group<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Next Topics<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-3-bonding-structure\/\">Bonding &amp; Structure<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/\">Organic Chemistry &amp; Alkanes<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-5-alkenes\/\">Alkenes<\/a>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n<\/aside>\r\n\r\n<script>\r\n(function() {\r\n  function normalisePath(path) {\r\n    return String(path || '')\r\n      .split('?')[0]\r\n      .split('#')[0]\r\n      .replace(\/\\\/+$\/, '')\r\n      .toLowerCase();\r\n  }\r\n\r\n  function highlightActive() {\r\n    var sidebar = document.querySelector('.ols-sidebar');\r\n    if (!sidebar) return false;\r\n\r\n    var currentPath = normalisePath(window.location.pathname);\r\n    var links = sidebar.querySelectorAll('a[href]');\r\n    var matched = null;\r\n    var matchedLength = 0;\r\n\r\n    sidebar.querySelectorAll('.active, .active-main, .parent-active').forEach(function(item) {\r\n      item.classList.remove('active', 'active-main', 'parent-active');\r\n    });\r\n\r\n    sidebar.querySelectorAll('a[data-ols-disabled-parent=\"1\"], a[aria-current]').forEach(function(a) {\r\n      a.removeAttribute('aria-current');\r\n      a.removeAttribute('tabindex');\r\n      a.removeAttribute('data-ols-disabled-parent');\r\n    });\r\n\r\n    links.forEach(function(a) {\r\n      try {\r\n        var href = a.getAttribute('href');\r\n\r\n        if (!href || href === '#' || href.charAt(0) === '#') {\r\n          return;\r\n        }\r\n\r\n        var linkPath = normalisePath(new URL(href, window.location.origin).pathname);\r\n\r\n        if (!linkPath) {\r\n          return;\r\n        }\r\n\r\n        if (currentPath === linkPath || currentPath.indexOf(linkPath + '\/') === 0) {\r\n          if (linkPath.length > matchedLength) {\r\n            matched = a;\r\n            matchedLength = linkPath.length;\r\n          }\r\n        }\r\n      } catch(e) {}\r\n    });\r\n\r\n    if (matched) {\r\n      var matchedLi = matched.closest('li');\r\n      var parentSub = matched.closest('.ols-subtopic-list');\r\n\r\n      if (parentSub) {\r\n        if (matchedLi) {\r\n          matchedLi.classList.add('active');\r\n          matched.setAttribute('aria-current', 'page');\r\n        }\r\n\r\n        var parentLi = parentSub.closest('li');\r\n\r\n        if (parentLi) {\r\n          parentLi.classList.add('parent-active', 'active-main');\r\n\r\n          var parentLink = parentLi.querySelector(':scope > a');\r\n\r\n          if (parentLink) {\r\n            parentLink.setAttribute('aria-current', 'true');\r\n            parentLink.setAttribute('tabindex', '-1');\r\n            parentLink.setAttribute('data-ols-disabled-parent', '1');\r\n          }\r\n        }\r\n      } else {\r\n        if (matchedLi) {\r\n          matchedLi.classList.add('parent-active', 'active-main');\r\n          matched.setAttribute('aria-current', 'page');\r\n          matched.setAttribute('tabindex', '-1');\r\n          matched.setAttribute('data-ols-disabled-parent', '1');\r\n        }\r\n      }\r\n    }\r\n\r\n    return true;\r\n  }\r\n\r\n  if (!highlightActive()) {\r\n    document.addEventListener('DOMContentLoaded', highlightActive);\r\n  }\r\n})();\r\n<\/script>\r\n\n\n  <main class=\"ols-main\">\n      <nav class=\"ols-breadcrumbs\" aria-label=\"Breadcrumb\">\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\">Revision Notes<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\">A Level Chemistry<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Edexcel International<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/\">Topic 2 Atomic Structure &amp; The Periodic Table<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/\">Mass Spectrometry<\/a> \/\n        <span>Identifying Compounds from Mass Spectra<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Identifying Compounds from Mass Spectra<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to using the molecular ion peak and peak pattern in a mass spectrum to help identify an unknown compound.<\/p>\n\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Exam board: Edexcel International<\/div>\n          <div class=\"ols-badge\">Topic 2: Atomic Structure &amp; The Periodic Table<\/div>\n          <div class=\"ols-badge\">Level: A Level Chemistry<\/div>\n        <\/div>\n\n        <div class=\"ols-author\">\n\n    <img decoding=\"async\"\n      class=\"ols-author-avatar-img\"\n      src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\"\n      alt=\"Dr. Mohammed Al-Fatah\"\n    >\n\n    <div class=\"ols-author-content\">\n\n      <h2 class=\"ols-author-title\">\n        Written by: Dr. Mohammed Al-Fatah\n      <\/h2>\n\n      <p class=\"ols-author-description\">\n        Chemistry specialist revision notes for A Level Chemistry.\n      <\/p>\n\n      <a class=\"ols-linkedin-pill\" href=\"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\" target=\"_blank\" rel=\"noopener noreferrer\">\n\n        <svg class=\"ols-linkedin-icon\" viewBox=\"0 0 24 24\" fill=\"currentColor\" aria-hidden=\"true\">\n          <path d=\"M4.98 3.5C4.98 4.88 3.86 6 2.48 6S0 4.88 0 3.5 1.12 1 2.48 1s2.5 1.12 2.5 2.5zM.5 8h4V24h-4V8zm7 0h3.8v2.2h.1c.5-.9 1.8-2.2 3.9-2.2 4.2 0 5 2.8 5 6.4V24h-4v-7.6c0-1.8 0-4.2-2.6-4.2s-3 2-3 4v7.8h-4V8z\"\/>\n        <\/svg>\n\n        View LinkedIn Profile\n\n      <\/a>\n\n    <\/div>\n\n  <\/div>\n      <\/header>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">1<\/div><h2>What Does Identifying a Compound Mean?<\/h2><\/div>\n        <p>Mass spectrometry can be used to help <strong>identify unknown compounds<\/strong> by analysing the pattern of peaks in their spectra.<\/p>\n        <p>The most important starting point is often the <strong>molecular ion peak<\/strong>, also called the <strong>M<sup>+<\/sup> peak<\/strong>. This peak is caused by the molecular ion formed when one electron is removed from the molecule.<\/p>\n        <div class=\"ols-definition-box\">\n          <p><strong>Molecular ion:<\/strong> the positive ion formed when a molecule loses one electron, usually written as M<sup>+<\/sup>.<\/p>\n        <\/div>\n        <div class=\"ols-key-box\"><p><strong>Key idea:<\/strong> for a 1+ ion, the m\/z value of the molecular ion peak is equal to the relative molecular mass of the compound.<\/p><\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">2<\/div><h2>Use the Molecular Ion Peak to Find Molecular Mass<\/h2><\/div>\n        <p>When a sample is bombarded with electrons in the mass spectrometer, some molecules lose an electron and form molecular ions.<\/p>\n\n        <div class=\"ols-formula-box\">\n          <p>Molecule + electron beam &rarr; M<sup>+<\/sup> + e<sup>&#8211;<\/sup><\/p>\n          <small>The molecular ion normally has a single positive charge, so m\/z matches the molecular mass.<\/small>\n        <\/div>\n\n        <p>In a mass spectrum, the molecular ion peak is usually the peak with the <strong>highest significant m\/z value<\/strong>. Small M+1 peaks may appear just above it because of naturally occurring isotopes such as carbon-13, so these are usually ignored when finding the main molecular mass.<\/p>\n\n        <div class=\"ols-key-box\"><p><strong>Exam focus:<\/strong> use the highest significant molecular ion peak, not a small M+1 isotope peak, when identifying the molecular mass.<\/p><\/div>\n      <\/article>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">3<\/div><h2>Read the Axes Before Interpreting the Spectrum<\/h2><\/div>\n        <p>The <strong>x-axis<\/strong> in a mass spectrum shows the mass-to-charge ratio, written as <strong>m\/z<\/strong>. The <strong>y-axis<\/strong> shows the relative abundance of ions, often expressed as a percentage.<\/p>\n        <p>For most introductory A Level examples, the ions are assumed to have a <strong>1+ charge<\/strong>. This means the m\/z value can be interpreted directly as the mass of that ion.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Feature<\/th>\n                <th>Meaning<\/th>\n                <th>How it helps identify a compound<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Feature\">m\/z value<\/td>\n                <td data-label=\"Meaning\">Mass-to-charge ratio of an ion<\/td>\n                <td data-label=\"How it helps identify a compound\">For 1+ ions, it gives the mass of the ion.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Feature\">Relative abundance<\/td>\n                <td data-label=\"Meaning\">How common each ion is compared with the others<\/td>\n                <td data-label=\"How it helps identify a compound\">The peak pattern can support a suggested structure.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Feature\">M<sup>+<\/sup> peak<\/td>\n                <td data-label=\"Meaning\">Peak caused by the molecular ion<\/td>\n                <td data-label=\"How it helps identify a compound\">Its m\/z value gives the relative molecular mass.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card orange\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">4<\/div><h2>Worked Example: Identifying Ethanol<\/h2><\/div>\n        <p>The mass spectrum of an unknown alcohol shows a molecular ion peak at <strong>m\/z 46<\/strong>. Assuming the molecular ion has a 1+ charge, this means the relative molecular mass of the compound is <strong>46<\/strong>.<\/p>\n\n        <div class=\"ols-worked-grid\">\n          <div class=\"ols-worked-step\">\n            <h3>Step 1: Find the molecular ion peak<\/h3>\n            <p>The molecular ion peak is at m\/z 46, so the compound has M<sub>r<\/sub> = 46.<\/p>\n          <\/div>\n          <div class=\"ols-worked-step\">\n            <h3>Step 2: Compare with possible alcohols<\/h3>\n            <p>Ethanol has formula C<sub>2<\/sub>H<sub>5<\/sub>OH, or C<sub>2<\/sub>H<sub>6<\/sub>O.<\/p>\n          <\/div>\n          <div class=\"ols-worked-step\">\n            <h3>Step 3: Calculate the relative molecular mass<\/h3>\n            <p>(2 &times; 12.0) + (6 &times; 1.0) + 16.0 = <strong>46.0<\/strong><\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-formula-box\">\n          <p>M<sub>r<\/sub> of ethanol = 46.0<\/p>\n          <small>This matches the molecular ion peak at m\/z 46.<\/small>\n        <\/div>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Mass-spectrometry-analysis-of-ethanol.png\" alt=\"Mass spectrometry analysis of ethanol showing the molecular ion peak used to identify the compound\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>The molecular ion peak at m\/z 46 matches the relative molecular mass of ethanol, C<sub>2<\/sub>H<sub>5<\/sub>OH.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">5<\/div><h2>Use the Peak Pattern to Support the Identity<\/h2><\/div>\n        <p>The molecular ion peak gives the molecular mass, but a mass spectrum usually contains other peaks as well. These arise from <strong>fragment ions<\/strong>, produced when the molecular ion breaks apart.<\/p>\n        <p>Fragment peaks can help distinguish compounds with the same molecular mass. For example, different alcohols may produce different fragment ion patterns even if they have the same molecular formula.<\/p>\n        <div class=\"ols-key-box\"><p><strong>Key idea:<\/strong> molecular ion peak first, then peak pattern. The molecular ion peak gives molecular mass, while fragment peaks help support the identity or structure.<\/p><\/div>\n      <\/article>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">6<\/div><h2>Common Exam Points<\/h2><\/div>\n        <p>These points help avoid common mistakes when interpreting mass spectra of unknown compounds.<\/p>\n\n        <div class=\"ols-rule-list\">\n          <div class=\"ols-rule-item\"><h3>Do not confuse the base peak with the molecular ion peak<\/h3><p>The base peak is the tallest peak. The molecular ion peak is the peak caused by the whole molecule after losing one electron. They are not always the same peak.<\/p><\/div>\n          <div class=\"ols-rule-item\"><h3>Use the highest significant m\/z value<\/h3><p>The molecular ion peak is usually at the highest significant m\/z value. Small M+1 peaks can occur due to carbon-13 and should not normally be used as the main molecular mass.<\/p><\/div>\n          <div class=\"ols-rule-item\"><h3>State the charge assumption<\/h3><p>For a 1+ molecular ion, m\/z is equal to the molecular mass. If the charge were different, the relationship would change.<\/p><\/div>\n          <div class=\"ols-rule-item\"><h3>Show the molecular mass calculation<\/h3><p>When suggesting a compound, calculate its M<sub>r<\/sub> and compare it directly with the molecular ion peak.<\/p><\/div>\n        <\/div>\n      <\/article>\n\n      <section class=\"ols-h5p-card\">\n        <h2>Check Your Understanding<\/h2>\n        <p>Use these short H5P tasks to test how the molecular ion peak and peak pattern are used to identify unknown compounds from mass spectra.<\/p>\n\n        <div class=\"ols-h5p-grid\">\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-255\" class=\"h5p-iframe\" data-content-id=\"255\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T2.2.4.1 Drag: Identifying Compounds from Mass Spectra Key Concepts\"><\/iframe><\/div><\/div>\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-256\" class=\"h5p-iframe\" data-content-id=\"256\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T2.2.4.2 MCQ: Molecular Ion Peak and Molecular Mass\"><\/iframe><\/div><\/div>\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-257\" class=\"h5p-iframe\" data-content-id=\"257\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T2.2.4.3 MCQ: Identifying Ethanol from a Mass Spectrum\"><\/iframe><\/div><\/div>\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-258\" class=\"h5p-iframe\" data-content-id=\"258\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T2.2.4.4 MCQ: Base Peak and Molecular Ion Peak\"><\/iframe><\/div><\/div>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-quicksnap-card\">\n        <h2>QuickSnap Summary<\/h2>\n        <p>Identifying a compound from a mass spectrum starts with the molecular ion peak, then uses the wider peak pattern to support the proposed identity.<\/p>\n\n        <div class=\"ols-snap-list\">\n          <div class=\"ols-snap-item\"><div class=\"ols-snap-number\">1<\/div><p>Find the molecular ion, M<sup>+<\/sup>, peak in the spectrum.<\/p><\/div>\n          <div class=\"ols-snap-item\"><div class=\"ols-snap-number\">2<\/div><p>For a 1+ ion, use the m\/z value of the molecular ion peak as the molecular mass.<\/p><\/div>\n          <div class=\"ols-snap-item\"><div class=\"ols-snap-number\">3<\/div><p>Compare the molecular mass with possible compounds by calculating their M<sub>r<\/sub> values.<\/p><\/div>\n          <div class=\"ols-snap-item\"><div class=\"ols-snap-number\">4<\/div><p>Use fragment peaks and the overall peak pattern as supporting evidence for the proposed compound.<\/p><\/div>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-course-cta-atomic-structure\" id=\"olsCourseCtaAtomicStructure002\">\n  <style>\n    .ols-course-cta-atomic-structure,\n    .ols-course-cta-atomic-structure * {\n      box-sizing: border-box;\n    }\n\n    .ols-course-cta-atomic-structure {\n      --navy: #1C244B;\n      --blue: #2563eb;\n      --body-text: #1f2937;\n      --grey-text: #667085;\n      --border: rgba(28, 36, 75, 0.14);\n      --shadow: 0 18px 45px rgba(28, 36, 75, 0.12);\n      --inner-shadow: 0 10px 26px rgba(28, 36, 75, 0.08);\n\n      width: 100%;\n      margin: 30px 0 24px;\n      font-family: Poppins, Arial, sans-serif;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-card {\n      overflow: hidden;\n      border-radius: 30px;\n      border: 1px solid var(--border);\n      background:\n        radial-gradient(circle at top left, rgba(37, 99, 235, 0.16), transparent 34%),\n        linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n      box-shadow: var(--shadow);\n      padding: 30px;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-top {\n      display: grid;\n      grid-template-columns: minmax(260px, 0.9fr) minmax(0, 1.1fr);\n      gap: 28px;\n      align-items: center;\n      margin-bottom: 24px;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-image-link {\n      display: block;\n      text-decoration: none;\n      border-radius: 24px;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-image {\n      width: 100%;\n      border-radius: 24px;\n      overflow: hidden;\n      border: 1px solid var(--border);\n      background: #ffffff;\n      box-shadow: var(--inner-shadow);\n      transition:\n        transform 0.35s ease,\n        box-shadow 0.35s ease;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-image img {\n      width: 100%;\n      height: auto;\n      display: block;\n      transition: transform 0.45s ease;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-image-link:hover .ols-course-cta-image {\n      transform: translateY(-8px) scale(1.015);\n      box-shadow:\n        0 26px 60px rgba(28, 36, 75, 0.18),\n        0 0 0 1px rgba(37, 99, 235, 0.12);\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-image-link:hover .ols-course-cta-image img {\n      transform: scale(1.03);\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-header-row {\n      display: flex;\n      flex-wrap: wrap;\n      align-items: center;\n      justify-content: space-between;\n      gap: 14px;\n      margin-bottom: 18px;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-kicker {\n      display: inline-flex;\n      align-items: center;\n      padding: 8px 14px;\n      border-radius: 999px;\n      background: #ffffff;\n      border: 1px solid rgba(37, 99, 235, 0.18);\n      color: var(--blue);\n      font-size: 14px;\n      line-height: 1.2;\n      font-weight: 700;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-course-cta-atomic-structure h2 {\n      margin: 0 0 14px;\n      font-size: clamp(28px, 3.5vw, 42px);\n      line-height: 1.15;\n      font-weight: 800;\n      letter-spacing: -0.03em;\n      color: #111827;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-intro-stats {\n      display: grid;\n      grid-template-columns: minmax(0, 1.08fr) minmax(320px, 0.92fr);\n      gap: 24px;\n      align-items: stretch;\n      margin: 0 0 30px;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-intro {\n      margin: 0;\n      color: var(--body-text);\n      font-size: clamp(16px, 1.4vw, 18px);\n      line-height: 1.7;\n      font-weight: 300;\n      align-self: center;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-stats {\n      display: grid;\n      grid-template-columns: repeat(2, minmax(0, 1fr));\n      gap: 14px;\n      margin: 0;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-stat {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 16px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-stat span {\n      display: block;\n      margin-bottom: 6px;\n      color: var(--grey-text);\n      font-size: 13px;\n      line-height: 1.35;\n      font-weight: 700;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-stat strong {\n      display: block;\n      color: var(--navy);\n      font-size: 18px;\n      line-height: 1.35;\n      font-weight: 800;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-features {\n      display: grid;\n      grid-template-columns: repeat(2, minmax(0, 1fr));\n      gap: 14px;\n      margin: 0 0 30px;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-feature {\n      background: rgba(255, 255, 255, 0.78);\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 16px 18px;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-feature h3 {\n      margin: 0 0 6px;\n      color: var(--navy);\n      font-size: 18px;\n      line-height: 1.3;\n      font-weight: 800;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-feature p {\n      margin: 0;\n      color: var(--body-text);\n      font-size: 15px;\n      line-height: 1.6;\n      font-weight: 300;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-animation-wrap {\n      position: relative;\n      margin: 0 0 30px;\n      border-radius: 0;\n      overflow: visible;\n      border: 0;\n      background: transparent;\n      box-shadow: none;\n      padding: 0;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-animation-title {\n      margin: 0 0 18px;\n      text-align: center;\n      color: var(--navy);\n      font-size: clamp(26px, 3.2vw, 40px);\n      line-height: 1.15;\n      font-weight: 700;\n      letter-spacing: -0.03em;\n      text-shadow: -9px 0 9px rgba(28, 36, 75, 0.10);\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-frame-shell {\n      position: relative;\n      width: 100%;\n      height: 620px;\n      border-radius: 24px;\n      overflow: hidden;\n      background:\n        radial-gradient(circle at top left, rgba(70, 127, 247, 0.14), transparent 34%),\n        linear-gradient(135deg, #f8fbff 0%, #e9efff 100%);\n      box-shadow: 0 24px 64px rgba(28, 36, 75, 0.18);\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-frame-shell iframe {\n      display: block;\n      width: 100%;\n      height: 100%;\n      border: 0;\n      background: #e9efff;\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-start-overlay {\n      position: absolute;\n      inset: 0;\n      z-index: 5;\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      border: 0;\n      cursor: pointer;\n      background:\n        radial-gradient(circle at center, rgba(255, 255, 255, 0.26), rgba(28, 36, 75, 0.28)),\n        url(\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/04\/edexcel-international-a-level-chemistry-topic-2-atomic-structure-periodic-table-course-banner.jpg\");\n      background-size: cover;\n      background-position: center;\n      transition:\n        opacity 0.35s ease,\n        visibility 0.35s ease;\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-start-overlay::before {\n      content: \"\";\n      position: absolute;\n      inset: 0;\n      background: rgba(28, 36, 75, 0.30);\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-start-overlay.is-hidden {\n      opacity: 0;\n      visibility: hidden;\n      pointer-events: none;\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-start-content {\n      position: relative;\n      z-index: 2;\n      display: grid;\n      justify-items: center;\n      gap: 16px;\n      padding: 24px;\n      text-align: center;\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-play-circle {\n      width: 96px;\n      height: 96px;\n      border-radius: 50%;\n      background: #ffffff;\n      color: var(--navy);\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      box-shadow:\n        0 18px 40px rgba(28, 36, 75, 0.30),\n        0 0 0 12px rgba(255, 255, 255, 0.22);\n      animation: olsAnimationPlayPulse002 1.8s ease-in-out infinite;\n      transition:\n        transform 0.25s ease,\n        background 0.25s ease,\n        color 0.25s ease;\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-start-overlay:hover .ols-animation-play-circle {\n      transform: scale(1.08);\n      background: var(--navy);\n      color: #ffffff;\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-play-icon {\n      width: 0;\n      height: 0;\n      margin-left: 7px;\n      border-top: 18px solid transparent;\n      border-bottom: 18px solid transparent;\n      border-left: 28px solid currentColor;\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-start-text {\n      max-width: 540px;\n      margin: 0;\n      color: #ffffff;\n      font-size: clamp(20px, 3vw, 32px);\n      line-height: 1.2;\n      font-weight: 800;\n      text-shadow: 0 8px 20px rgba(0, 0, 0, 0.28);\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-pause-button {\n      position: absolute;\n      left: 16px;\n      bottom: 16px;\n      z-index: 7;\n      display: none;\n      align-items: center;\n      justify-content: center;\n      min-width: 92px;\n      padding: 10px 16px;\n      border: 0;\n      border-radius: 999px;\n      background: rgba(28, 36, 75, 0.92);\n      color: #ffffff;\n      font-family: Poppins, Arial, sans-serif;\n      font-size: 14px;\n      line-height: 1.2;\n      font-weight: 800;\n      cursor: pointer;\n      box-shadow: 0 12px 28px rgba(28, 36, 75, 0.24);\n      transition:\n        transform 0.2s ease,\n        background 0.2s ease,\n        box-shadow 0.2s ease;\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-pause-button:hover {\n      transform: translateY(-2px);\n      background: var(--blue);\n      box-shadow: 0 16px 34px rgba(37, 99, 235, 0.28);\n    }\n\n    .ols-course-cta-atomic-structure .ols-animation-pause-button.is-visible {\n      display: inline-flex;\n    }\n\n    @keyframes olsAnimationPlayPulse002 {\n      0% {\n        box-shadow:\n          0 18px 40px rgba(28, 36, 75, 0.30),\n          0 0 0 0 rgba(255, 255, 255, 0.40);\n      }\n\n      70% {\n        box-shadow:\n          0 18px 40px rgba(28, 36, 75, 0.30),\n          0 0 0 18px rgba(255, 255, 255, 0);\n      }\n\n      100% {\n        box-shadow:\n          0 18px 40px rgba(28, 36, 75, 0.30),\n          0 0 0 0 rgba(255, 255, 255, 0);\n      }\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-video-status {\n      margin: 14px 0 0;\n      text-align: center;\n      color: var(--grey-text);\n      font-size: 13px;\n      line-height: 1.5;\n      font-weight: 500;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-cta-bottom {\n      display: flex;\n      justify-content: center;\n      padding-top: 22px;\n      border-top: 1px solid var(--border);\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-button {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      padding: 15px 28px;\n      border-radius: 999px;\n      background: var(--navy);\n      color: #ffffff;\n      text-decoration: none;\n      font-size: 16px;\n      line-height: 1.2;\n      font-weight: 800;\n      box-shadow: 0 12px 26px rgba(28, 36, 75, 0.18);\n      transition:\n        transform 0.2s ease,\n        background 0.2s ease,\n        box-shadow 0.2s ease;\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-button:hover {\n      transform: translateY(-2px);\n      background: var(--blue);\n      color: #ffffff;\n      box-shadow: 0 16px 32px rgba(37, 99, 235, 0.24);\n    }\n\n    .ols-course-cta-atomic-structure .ols-course-button-top {\n      flex-shrink: 0;\n      padding: 12px 22px;\n      font-size: 15px;\n    }\n\n    @media (max-width: 900px) {\n      .ols-course-cta-atomic-structure .ols-course-cta-top {\n        grid-template-columns: 1fr;\n      }\n\n      .ols-course-cta-atomic-structure .ols-course-cta-image-link {\n        max-width: 520px;\n        margin: 0 auto;\n      }\n\n      .ols-course-cta-atomic-structure .ols-course-cta-intro-stats {\n        grid-template-columns: 1fr;\n      }\n\n      .ols-course-cta-atomic-structure .ols-animation-frame-shell {\n        height: 520px;\n      }\n    }\n\n    @media (max-width: 760px) {\n      .ols-course-cta-atomic-structure {\n        margin: 26px 0 22px;\n      }\n\n      .ols-course-cta-atomic-structure .ols-course-cta-card {\n        padding: 20px;\n        border-radius: 24px;\n      }\n\n      .ols-course-cta-atomic-structure .ols-course-cta-header-row {\n        align-items: stretch;\n      }\n\n      .ols-course-cta-atomic-structure .ols-course-button-top {\n        width: 100%;\n      }\n\n      .ols-course-cta-atomic-structure .ols-course-cta-stats,\n      .ols-course-cta-atomic-structure .ols-course-cta-features {\n        grid-template-columns: 1fr;\n      }\n\n      .ols-course-cta-atomic-structure .ols-course-animation-wrap {\n        padding: 0;\n        border-radius: 0;\n      }\n\n      .ols-course-cta-atomic-structure .ols-animation-frame-shell {\n        height: 420px;\n        border-radius: 18px;\n      }\n\n      .ols-course-cta-atomic-structure .ols-animation-play-circle {\n        width: 76px;\n        height: 76px;\n      }\n\n      .ols-course-cta-atomic-structure .ols-animation-play-icon {\n        border-top-width: 14px;\n        border-bottom-width: 14px;\n        border-left-width: 22px;\n      }\n\n      .ols-course-cta-atomic-structure .ols-animation-pause-button {\n        left: 12px;\n        bottom: 12px;\n        min-width: 84px;\n        padding: 9px 14px;\n        font-size: 13px;\n      }\n\n      .ols-course-cta-atomic-structure .ols-course-button {\n        width: 100%;\n      }\n    }\n  <\/style>\n\n  <div class=\"ols-course-cta-card\">\n\n    <div class=\"ols-course-cta-top\">\n\n      <a class=\"ols-course-cta-image-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/atomic-structure-and-periodic-table-edexcel-t2\/\" aria-label=\"Open the Edexcel International A Level Chemistry Topic 2 Atomic Structure and The Periodic Table course page\">\n\n        <div class=\"ols-course-cta-image\">\n          <img decoding=\"async\"\n            src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/04\/edexcel-international-a-level-chemistry-topic-2-atomic-structure-periodic-table-course-banner.jpg\"\n            alt=\"Edexcel International A Level Chemistry Topic 2 Atomic Structure and The Periodic Table course banner\"\n          >\n        <\/div>\n\n      <\/a>\n\n      <div class=\"ols-course-cta-content\">\n\n        <div class=\"ols-course-cta-header-row\">\n\n          <div class=\"ols-course-cta-kicker\">\n            Complete Topic 2 Atomic Structure &#038; The Periodic Table Course\n          <\/div>\n\n          <a class=\"ols-course-button ols-course-button-top\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/atomic-structure-and-periodic-table-edexcel-t2\/\">\n            View Course\n          <\/a>\n\n        <\/div>\n\n        <h2>\n          Master Atomic Structure and The Periodic Table for Edexcel International A Level Chemistry\n        <\/h2>\n\n      <\/div>\n\n    <\/div>\n\n    <div class=\"ols-course-cta-intro-stats\">\n\n      <p class=\"ols-course-cta-intro\">\n        Continue from these free revision notes into the full Topic 2 Atomic Structure and The Periodic Table course, with guided video teaching, diagnostic MCQ practice, teacher-marked short-answer questions and a specification assignment with a personalised progress report.\n      <\/p>\n\n      <div class=\"ols-course-cta-stats\">\n\n        <div class=\"ols-course-stat\">\n          <span>Guided learning<\/span>\n          <strong>18 hours<\/strong>\n        <\/div>\n\n        <div class=\"ols-course-stat\">\n          <span>Video lessons<\/span>\n          <strong>369 mins<\/strong>\n        <\/div>\n\n        <div class=\"ols-course-stat\">\n          <span>MCQ practice<\/span>\n          <strong>86 marks<\/strong>\n        <\/div>\n\n        <div class=\"ols-course-stat\">\n          <span>SAQ practice<\/span>\n          <strong>215 marks<\/strong>\n        <\/div>\n\n      <\/div>\n\n    <\/div>\n\n    <div class=\"ols-course-cta-features\">\n\n      <div class=\"ols-course-feature\">\n        <h3>Guided video teaching<\/h3>\n        <p>\n          Learn atomic structure, isotopes, mass spectrometry, ionisation energy, electron configuration and periodic trends through structured video lessons with worked examples and walkthroughs.\n        <\/p>\n      <\/div>\n\n      <div class=\"ols-course-feature\">\n        <h3>Instant MCQ feedback<\/h3>\n        <p>\n          Auto-marked MCQ quizzes provide immediate diagnostic feedback for every answer choice.\n        <\/p>\n      <\/div>\n\n      <div class=\"ols-course-feature\">\n        <h3>Teacher-marked SAQs<\/h3>\n        <p>\n          Submit written exam responses and receive chemistry specialist feedback with improvement guidance.\n        <\/p>\n      <\/div>\n\n      <div class=\"ols-course-feature\">\n        <h3>Progress tracking<\/h3>\n        <p>\n          Identify strengths and weaknesses across atomic structure, isotopes, mass spectrometry, ionisation energies, electron configuration and periodic trends with targeted reporting.\n        <\/p>\n      <\/div>\n\n    <\/div>\n\n    <div class=\"ols-course-animation-wrap\">\n\n      <h3 class=\"ols-course-animation-title\">\n        See how the course works\n      <\/h3>\n\n      <div class=\"ols-animation-frame-shell\">\n        <iframe\n          id=\"olsCourseAnimationFrame002\"\n          title=\"OLS course preview animation\"\n          loading=\"lazy\"\n          referrerpolicy=\"no-referrer\">\n        <\/iframe>\n\n        <button\n          class=\"ols-animation-start-overlay\"\n          id=\"olsCourseAnimationStart002\"\n          type=\"button\"\n          aria-label=\"Play OLS course preview animation\">\n          <span class=\"ols-animation-start-content\">\n            <span class=\"ols-animation-play-circle\" aria-hidden=\"true\">\n              <span class=\"ols-animation-play-icon\"><\/span>\n            <\/span>\n            <span class=\"ols-animation-start-text\">\n              Play course preview animation\n            <\/span>\n          <\/span>\n        <\/button>\n\n        <button\n          class=\"ols-animation-pause-button\"\n          id=\"olsCourseAnimationPause002\"\n          type=\"button\"\n          aria-label=\"Pause course preview animation\">\n          Pause\n        <\/button>\n      <\/div>\n\n      <p class=\"ols-course-video-status\">\n        Click play to start the course preview animation.\n      <\/p>\n\n    <\/div>\n\n    <div class=\"ols-course-cta-bottom\">\n\n      <a class=\"ols-course-button\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/atomic-structure-and-periodic-table-edexcel-t2\/\">\n        View Atomic Structure &#038; The Periodic Table Topic 2 Course\n      <\/a>\n\n    <\/div>\n\n  <\/div>\n\n  <template id=\"olsCourseAnimationTemplate002\">\n<!DOCTYPE html>\n<html lang=\"en\">\n<head>\n<meta charset=\"UTF-8\">\n<meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">\n<title>OLS Combined Promo Animation<\/title>\n\n<style>\n*{box-sizing:border-box;}\n\nhtml.ols-animation-paused *,\nhtml.ols-animation-paused *::before,\nhtml.ols-animation-paused *::after{\n  animation-play-state:paused!important;\n}\n\n:root{\n  --ols-video-screen-w:1180;\n  --ols-video-screen-h:664;\n  --ols-video-screen-scale:1;\n  --ols-mcq-screen-w:1360;\n  --ols-mcq-screen-h:1130;\n  --ols-mcq-screen-scale:1;\n  --ols-saq-screen-w:1360;\n  --ols-saq-screen-h:965;\n  --ols-saq-screen-scale:1;\n}\n\nhtml,\nbody{\n  width:100%;\n  height:100%;\n}\n\nbody{\n  margin:0;\n  overflow:hidden;\n  font-family:Poppins,Arial,sans-serif;\n  background:#e9efff;\n}\n\n.ols-combined-stage{\n  position:relative;\n  width:100vw;\n  height:100vh;\n  overflow:hidden;\n  background:\n    radial-gradient(circle at top left,rgba(70,127,247,0.14),transparent 34%),\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\n}\n\n.ols-scene{\n  position:absolute;\n  inset:0;\n  width:100vw;\n  height:100vh;\n  opacity:0;\n  visibility:hidden;\n  pointer-events:none;\n}\n\n.ols-scene.active{\n  opacity:1;\n  visibility:visible;\n  pointer-events:auto;\n}\n\n.ols-scene.fade-out{\n  animation:olsSceneFadeOut 0.85s ease forwards;\n}\n\n@keyframes olsSceneFadeOut{\n  to{\n    opacity:0;\n    visibility:hidden;\n  }\n}\n\n.ols-title-cursor{\n  display:inline-block;\n  width:5px;\n  height:0.85em;\n  background:#1C244B;\n  margin-left:8px;\n  transform:translateY(8px);\n  animation:olsBlink 0.8s infinite;\n}\n\n.cursor{\n  display:inline-block;\n  width:3px;\n  height:28px;\n  background:#1c244b;\n  margin-left:3px;\n  transform:translateY(5px);\n  animation:olsBlink 0.8s infinite;\n}\n\n@keyframes olsBlink{\n  0%,45%{opacity:1;}\n  46%,100%{opacity:0;}\n}\n\n.ols-video-stage,\n.ols-mcq-stage,\n.ols-saq-stage{\n  width:100vw;\n  height:100vh;\n  display:flex;\n  justify-content:center;\n  align-items:center;\n  padding:0;\n  overflow:hidden;\n  background:\n    radial-gradient(circle at top left,rgba(70,127,247,0.14),transparent 34%),\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\n}\n\n.ols-video-title-screen,\n.ols-mcq-intro-screen,\n.ols-saq-intro{\n  position:absolute;\n  inset:0;\n  z-index:50;\n  display:flex;\n  justify-content:center;\n  align-items:center;\n  background:\n    radial-gradient(circle at top left,rgba(70,127,247,0.14),transparent 34%),\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\n  opacity:1;\n  visibility:visible;\n  pointer-events:none;\n}\n\n.ols-video-title-screen.hide{animation:olsVideoTitleFadeOut 0.85s ease forwards;}\n.ols-mcq-intro-screen.hide{animation:olsMcqIntroFadeOut 0.85s ease forwards;}\n.ols-saq-intro.hide{animation:olsSaqIntroFadeOut 0.85s ease forwards;}\n\n@keyframes olsVideoTitleFadeOut{to{opacity:0;visibility:hidden;}}\n@keyframes olsMcqIntroFadeOut{to{opacity:0;visibility:hidden;}}\n@keyframes olsSaqIntroFadeOut{to{opacity:0;visibility:hidden;}}\n\n.ols-video-title-wrap,\n.ols-mcq-intro-title-wrap,\n.ols-saq-intro-title-wrap{\n  max-width:1250px;\n  padding:0 34px;\n  text-align:center;\n}\n\n.ols-video-title,\n.ols-mcq-intro-title,\n.ols-saq-intro-title{\n  margin:0;\n  font-family:Poppins,Arial,sans-serif;\n  font-size:clamp(52px,8vw,124px);\n  font-weight:600;\n  line-height:1.08;\n  color:#1C244B;\n  text-shadow:-9px 0 9px rgba(28,36,75,0.16);\n  letter-spacing:-0.045em;\n}\n\n#videoTitleText,\n#mcqIntroTitleText,\n#saqIntroTitleText{\n  white-space:pre-wrap;\n}\n\n.ols-video-scene{\n  width:100%;\n  height:100%;\n  display:flex;\n  justify-content:center;\n  align-items:center;\n  opacity:0;\n  visibility:hidden;\n}\n\n.ols-video-scene.show{\n  visibility:visible;\n  animation:olsVideoSceneIn 1s ease forwards;\n}\n\n@keyframes olsVideoSceneIn{to{opacity:1;}}\n\n.ols-video-scale-wrap{\n  width:calc(var(--ols-video-screen-w) * 1px);\n  height:calc(var(--ols-video-screen-h) * 1px);\n  transform:scale(var(--ols-video-screen-scale));\n  transform-origin:center center;\n  display:flex;\n  justify-content:center;\n  align-items:center;\n}\n\n.ols-video-card{\n  width:1180px;\n  height:664px;\n  border-radius:28px;\n  overflow:hidden;\n  background:#1C244B;\n  box-shadow:0 28px 80px rgba(28,36,75,0.28);\n  transform:translateY(24px) scale(0.96);\n  opacity:0;\n}\n\n.ols-video-scene.show .ols-video-card{\n  animation:olsVideoCardIn 1s cubic-bezier(.18,.89,.32,1.12) forwards;\n  animation-delay:0.2s;\n}\n\n@keyframes olsVideoCardIn{\n  to{\n    transform:translateY(0) scale(1);\n    opacity:1;\n  }\n}\n\n.ols-video-card video{\n  display:block;\n  width:100%;\n  height:100%;\n  aspect-ratio:16 \/ 9;\n  object-fit:cover;\n  border:0;\n}\n\n.ols-mcq-scale-wrap,\n.ols-saq-scale-wrap{\n  width:calc(var(--ols-mcq-screen-w) * 1px);\n  height:calc(var(--ols-mcq-screen-h) * 1px);\n  transform:scale(var(--ols-mcq-screen-scale));\n  transform-origin:center center;\n  display:flex;\n  justify-content:center;\n  align-items:flex-start;\n}\n\n.ols-saq-scale-wrap{\n  width:calc(var(--ols-saq-screen-w) * 1px);\n  height:calc(var(--ols-saq-screen-h) * 1px);\n  transform:scale(var(--ols-saq-screen-scale));\n}\n\n.ols-mcq-screen{\n  width:1360px;\n  height:1130px;\n  border-radius:22px;\n  overflow:hidden;\n  background:#eaf0ff;\n  box-shadow:0 26px 70px rgba(28,36,75,0.22);\n  opacity:0;\n  transform:translateY(24px) scale(0.96);\n}\n\n.ols-mcq-screen.show{\n  animation:olsMcqScreenEnter 1s ease forwards;\n}\n\n@keyframes olsMcqScreenEnter{\n  from{opacity:0;transform:translateY(24px) scale(0.96);}\n  to{opacity:1;transform:translateY(0) scale(1);}\n}\n\n.mcq-question-area{\n  background:#eaf0ff;\n  padding:28px 30px 30px;\n  position:relative;\n  height:610px;\n}\n\n.mcq-question-lead{\n  margin:0 0 14px;\n  font-size:24px;\n  line-height:1.35;\n  color:#111827;\n}\n\n.mcq-data-table{\n  border-collapse:collapse;\n  width:500px;\n  margin-bottom:8px;\n  font-size:21px;\n  color:#111827;\n}\n\n.mcq-data-table th,\n.mcq-data-table td{\n  border:1.5px solid #c9ced8;\n  padding:12px 18px;\n  text-align:center;\n}\n\n.mcq-data-table th{\n  background:#f2f2f2;\n  font-weight:700;\n}\n\n.mcq-data-table td{\n  background:#eaf0ff;\n}\n\n.mcq-question-main{\n  margin:6px 0 28px;\n  font-size:24px;\n  line-height:1.35;\n  color:#111827;\n}\n\n.mcq-options-wrap{\n  display:flex;\n  flex-direction:column;\n  gap:17px;\n  max-width:1200px;\n}\n\n.mcq-option-row{\n  display:flex;\n  align-items:center;\n  min-height:34px;\n  position:relative;\n}\n\n.mcq-radio{\n  width:28px;\n  height:28px;\n  border-radius:50%;\n  border:2px solid #6b7280;\n  margin-right:16px;\n  background:transparent;\n  position:relative;\n  flex:0 0 auto;\n}\n\n.mcq-radio::after{\n  content:\"\";\n  position:absolute;\n  inset:5px;\n  border-radius:50%;\n  background:#6b7280;\n  opacity:0;\n  transform:scale(0.4);\n  transition:opacity 0.25s ease,transform 0.25s ease;\n}\n\n.mcq-option-row.selected .mcq-radio::after{\n  opacity:1;\n  transform:scale(1);\n}\n\n.mcq-radio-ripple{\n  position:absolute;\n  left:14px;\n  top:50%;\n  width:28px;\n  height:28px;\n  border-radius:50%;\n  border:2px solid rgba(28,36,75,0.28);\n  transform:translate(-50%,-50%) scale(1);\n  opacity:0;\n  pointer-events:none;\n}\n\n.mcq-option-row.clicking .mcq-radio-ripple{\n  animation:mcqRipple 0.75s ease forwards;\n}\n\n@keyframes mcqRipple{\n  0%{opacity:0.65;transform:translate(-50%,-50%) scale(1);}\n  100%{opacity:0;transform:translate(-50%,-50%) scale(2.5);}\n}\n\n.mcq-option-label{\n  font-size:23px;\n  color:#111827;\n}\n\n.mcq-specific-feedback{\n  display:inline-flex;\n  align-items:center;\n  margin-left:18px;\n  min-height:38px;\n  opacity:0;\n  transform:translateX(-8px);\n}\n\n.mcq-specific-feedback.show{\n  opacity:1;\n  transform:translateX(0);\n  transition:opacity 0.35s ease,transform 0.35s ease;\n}\n\n.mcq-cross-icon{\n  width:26px;\n  height:26px;\n  border-radius:50%;\n  border:2px solid #d83255;\n  color:#d83255;\n  display:inline-flex;\n  justify-content:center;\n  align-items:center;\n  font-size:18px;\n  font-weight:700;\n  margin-right:12px;\n  opacity:0;\n  transform:scale(0.4);\n}\n\n.mcq-cross-icon.show{\n  animation:mcqCrossPop 0.35s ease forwards;\n}\n\n@keyframes mcqCrossPop{\n  70%{opacity:1;transform:scale(1.18);}\n  100%{opacity:1;transform:scale(1);}\n}\n\n.mcq-specific-feedback-text{\n  display:inline-block;\n  background:#fff4b8;\n  color:#111827;\n  padding:8px 16px;\n  font-size:22px;\n  line-height:1.35;\n  min-width:850px;\n  min-height:44px;\n}\n\n.mcq-submit-button{\n  position:absolute;\n  right:34px;\n  bottom:30px;\n  border:0;\n  border-radius:999px;\n  background:#1C244B;\n  color:#ffffff;\n  padding:14px 28px;\n  font-size:18px;\n  font-weight:600;\n  box-shadow:0 14px 32px rgba(28,36,75,0.25);\n  cursor:default;\n  transition:transform 0.2s ease,box-shadow 0.2s ease,background 0.2s ease;\n}\n\n.mcq-submit-button.clicked{\n  transform:translateY(2px) scale(0.97);\n  background:#26315f;\n  box-shadow:0 7px 18px rgba(28,36,75,0.22);\n}\n\n.mcq-general-feedback{\n  height:520px;\n  background:#fff3c9;\n  color:#8a6a00;\n  padding:26px 30px 28px;\n  font-size:23px;\n  line-height:1.34;\n  opacity:0;\n  transform:translateY(20px);\n  transition:opacity 0.7s ease,transform 0.7s ease;\n  overflow:hidden;\n}\n\n.mcq-general-feedback.show{\n  opacity:1;\n  transform:translateY(0);\n}\n\n#mcqGeneralText{\n  white-space:pre-wrap;\n}\n\n.mcq-specific-cursor{background:#111827;}\n.mcq-general-cursor{background:#8a6a00;}\n\n.ols-saq-screen{\n  width:1360px;\n  height:965px;\n  border-radius:22px;\n  overflow:hidden;\n  background:#eaf0ff;\n  box-shadow:0 26px 70px rgba(28,36,75,0.22);\n  opacity:0;\n  transform:translateY(24px) scale(0.96);\n}\n\n.ols-saq-screen.show{\n  animation:olsSaqScreenEnter 1s ease forwards;\n}\n\n@keyframes olsSaqScreenEnter{\n  from{opacity:0;transform:translateY(24px) scale(0.96);}\n  to{opacity:1;transform:translateY(0) scale(1);}\n}\n\n.saq-question-area{\n  height:335px;\n  background:#eaf0ff;\n  padding:30px 40px 32px;\n}\n\n.saq-question-text{\n  font-size:25px;\n  line-height:1.42;\n  color:#111827;\n  margin-bottom:22px;\n}\n\n.saq-student-box{\n  height:195px;\n  background:#f3f4f6;\n  border:2px solid #cfd6e3;\n  border-radius:8px;\n  padding:23px 26px;\n  font-size:24px;\n  line-height:1.55;\n  color:#4b5563;\n  position:relative;\n  overflow:hidden;\n}\n\n.saq-teacher-feedback{\n  height:630px;\n  background:#dff3e6;\n  color:#075f3b;\n  padding:28px 40px 30px;\n  font-size:23px;\n  line-height:1.47;\n  opacity:0;\n  transform:translateY(20px);\n  transition:opacity 0.7s ease,transform 0.7s ease;\n  overflow:hidden;\n}\n\n.saq-teacher-feedback.show{\n  opacity:1;\n  transform:translateY(0);\n}\n\n#saqTeacherText{\n  white-space:pre-wrap;\n}\n\n.saq-teacher-cursor{\n  background:#075f3b;\n}\n\n@media(max-width:900px){\n  .ols-video-title,\n  .ols-mcq-intro-title,\n  .ols-saq-intro-title{\n    font-size:clamp(42px,11vw,78px);\n    line-height:1.12;\n  }\n\n  .ols-title-cursor{\n    width:4px;\n    margin-left:6px;\n  }\n\n  .ols-video-card{\n    border-radius:20px;\n  }\n}\n<\/style>\n<\/head>\n\n<body>\n<div class=\"ols-combined-stage\">\n\n  <section id=\"sceneVideo\" class=\"ols-scene active\">\n    <div class=\"ols-video-stage\">\n      <div id=\"videoTitleScreen\" class=\"ols-video-title-screen\">\n        <div class=\"ols-video-title-wrap\">\n          <h1 class=\"ols-video-title\">\n            <span id=\"videoTitleText\"><\/span><span id=\"videoTitleCursor\" class=\"ols-title-cursor\"><\/span>\n          <\/h1>\n        <\/div>\n      <\/div>\n\n      <section id=\"videoScene\" class=\"ols-video-scene\">\n        <div class=\"ols-video-scale-wrap\">\n          <div class=\"ols-video-card\">\n            <video\n              id=\"lessonVideo\"\n              src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Virtual-Lesson.mp4\"\n              muted\n              playsinline\n              preload=\"auto\">\n            <\/video>\n          <\/div>\n        <\/div>\n      <\/section>\n    <\/div>\n  <\/section>\n\n  <section id=\"sceneMcq\" class=\"ols-scene\">\n    <div class=\"ols-mcq-stage\">\n      <div id=\"mcqIntroScreen\" class=\"ols-mcq-intro-screen\">\n        <div class=\"ols-mcq-intro-title-wrap\">\n          <h1 class=\"ols-mcq-intro-title\">\n            <span id=\"mcqIntroTitleText\"><\/span><span id=\"mcqIntroTitleCursor\" class=\"ols-title-cursor\"><\/span>\n          <\/h1>\n        <\/div>\n      <\/div>\n\n      <div class=\"ols-mcq-scale-wrap\">\n        <main id=\"mcqScreen\" class=\"ols-mcq-screen\">\n          <section class=\"mcq-question-area\">\n            <p class=\"mcq-question-lead\">Some successive ionisation energies for element X are shown.<\/p>\n\n            <table class=\"mcq-data-table\">\n              <thead>\n                <tr>\n                  <th>Ionisation energy<\/th>\n                  <th>Value \/ kJ mol<sup>\u22121<\/sup><\/th>\n                <\/tr>\n              <\/thead>\n              <tbody>\n                <tr><td>1st<\/td><td>738<\/td><\/tr>\n                <tr><td>2nd<\/td><td>1451<\/td><\/tr>\n                <tr><td>3rd<\/td><td>7733<\/td><\/tr>\n                <tr><td>4th<\/td><td>10543<\/td><\/tr>\n              <\/tbody>\n            <\/table>\n\n            <p class=\"mcq-question-main\">Which formula is most likely for the fluoride of element X?<\/p>\n\n            <div class=\"mcq-options-wrap\">\n              <div id=\"mcqWrongOption\" class=\"mcq-option-row\">\n                <span class=\"mcq-radio\"><\/span>\n                <span class=\"mcq-radio-ripple\"><\/span>\n                <span class=\"mcq-option-label\">XF<\/span>\n\n                <span id=\"mcqSpecificFeedback\" class=\"mcq-specific-feedback\">\n                  <span id=\"mcqCrossIcon\" class=\"mcq-cross-icon\">\u00d7<\/span>\n                  <span class=\"mcq-specific-feedback-text\">\n                    <span id=\"mcqSpecificText\"><\/span><span id=\"mcqSpecificCursor\" class=\"cursor mcq-specific-cursor\" style=\"display:none;\"><\/span>\n                  <\/span>\n                <\/span>\n              <\/div>\n\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">XF<sub>2<\/sub><\/span><\/div>\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">XF<sub>3<\/sub><\/span><\/div>\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">XF<sub>4<\/sub><\/span><\/div>\n            <\/div>\n\n            <button id=\"mcqSubmitButton\" class=\"mcq-submit-button\">Submit answer<\/button>\n          <\/section>\n\n          <section id=\"mcqGeneralFeedback\" class=\"mcq-general-feedback\">\n            <span id=\"mcqGeneralText\"><\/span><span id=\"mcqGeneralCursor\" class=\"cursor mcq-general-cursor\" style=\"display:none;\"><\/span>\n          <\/section>\n        <\/main>\n      <\/div>\n    <\/div>\n  <\/section>\n\n  <section id=\"sceneSaq\" class=\"ols-scene\">\n    <div class=\"ols-saq-stage\">\n      <div id=\"saqIntro\" class=\"ols-saq-intro\">\n        <div class=\"ols-saq-intro-title-wrap\">\n          <h1 class=\"ols-saq-intro-title\">\n            <span id=\"saqIntroTitleText\"><\/span><span id=\"saqIntroTitleCursor\" class=\"ols-title-cursor\"><\/span>\n          <\/h1>\n        <\/div>\n      <\/div>\n\n      <div class=\"ols-saq-scale-wrap\">\n        <main id=\"saqScreen\" class=\"ols-saq-screen\">\n          <section class=\"saq-question-area\">\n            <div class=\"saq-question-text\">\n              <strong>(ii)<\/strong>&nbsp;&nbsp; First ionisation energy generally increases across Period 3.<br>\n              Explain this trend in terms of nuclear charge, shielding and atomic radius.\n            <\/div>\n\n            <div class=\"saq-student-box\">\n              <span id=\"saqStudentText\"><\/span><span id=\"saqStudentCursor\" class=\"cursor\"><\/span>\n            <\/div>\n          <\/section>\n\n          <section id=\"saqTeacherFeedback\" class=\"saq-teacher-feedback\">\n            <span id=\"saqTeacherText\"><\/span><span id=\"saqTeacherCursor\" class=\"cursor saq-teacher-cursor\" style=\"display:none;\"><\/span>\n          <\/section>\n        <\/main>\n      <\/div>\n    <\/div>\n  <\/section>\n\n<\/div>\n\n<script>\n(function(){\n  const nativeSetTimeout=window.setTimeout.bind(window);\n  const nativeClearTimeout=window.clearTimeout.bind(window);\n  let nextTimerId=1;\n  let paused=false;\n  const timers=new Map();\n\n  function runTimer(timerId){\n    const timer=timers.get(timerId);\n\n    if(!timer || timer.cleared){\n      return;\n    }\n\n    timers.delete(timerId);\n    timer.callback();\n  }\n\n  window.setTimeout=function(callback,delay){\n    const timerId=nextTimerId++;\n    const safeDelay=Math.max(0,Number(delay) || 0);\n\n    const timer={\n      callback:callback,\n      delay:safeDelay,\n      remaining:safeDelay,\n      startedAt:Date.now(),\n      nativeId:null,\n      cleared:false\n    };\n\n    if(paused){\n      timer.startedAt=null;\n    }else{\n      timer.nativeId=nativeSetTimeout(function(){\n        runTimer(timerId);\n      },safeDelay);\n    }\n\n    timers.set(timerId,timer);\n    return timerId;\n  };\n\n  window.clearTimeout=function(timerId){\n    const timer=timers.get(timerId);\n\n    if(timer){\n      timer.cleared=true;\n\n      if(timer.nativeId!==null){\n        nativeClearTimeout(timer.nativeId);\n      }\n\n      timers.delete(timerId);\n      return;\n    }\n\n    nativeClearTimeout(timerId);\n  };\n\n  function pauseVideos(){\n    document.querySelectorAll(\"video\").forEach(function(video){\n      if(!video.paused && !video.ended){\n        video.dataset.olsWasPlaying=\"1\";\n        video.pause();\n      }\n    });\n  }\n\n  function resumeVideos(){\n    document.querySelectorAll(\"video\").forEach(function(video){\n      if(video.dataset.olsWasPlaying===\"1\"){\n        delete video.dataset.olsWasPlaying;\n\n        const playPromise=video.play();\n\n        if(playPromise!==undefined){\n          playPromise.catch(function(){});\n        }\n      }\n    });\n  }\n\n  function pauseAnimation(){\n    if(paused){\n      return \"paused\";\n    }\n\n    paused=true;\n    document.documentElement.classList.add(\"ols-animation-paused\");\n\n    timers.forEach(function(timer){\n      if(timer.nativeId!==null){\n        nativeClearTimeout(timer.nativeId);\n        timer.nativeId=null;\n      }\n\n      if(timer.startedAt!==null){\n        timer.remaining=Math.max(0,timer.delay-(Date.now()-timer.startedAt));\n        timer.startedAt=null;\n      }\n    });\n\n    pauseVideos();\n    return \"paused\";\n  }\n\n  function resumeAnimation(){\n    if(!paused){\n      return \"playing\";\n    }\n\n    paused=false;\n    document.documentElement.classList.remove(\"ols-animation-paused\");\n\n    timers.forEach(function(timer,timerId){\n      timer.startedAt=Date.now();\n      timer.delay=timer.remaining;\n      timer.nativeId=nativeSetTimeout(function(){\n        runTimer(timerId);\n      },timer.remaining);\n    });\n\n    resumeVideos();\n    return \"playing\";\n  }\n\n  window.olsToggleAnimationPause=function(){\n    if(paused){\n      return resumeAnimation();\n    }\n\n    return pauseAnimation();\n  };\n\n  window.olsPauseAnimation=pauseAnimation;\n  window.olsResumeAnimation=resumeAnimation;\n})();\n\nfunction typeWriter(target,text,speed,callback){\n  let i=0;\n\n  function typing(){\n    if(i<text.length){\n      const char=text.charAt(i);\n      target.textContent+=char;\n      i++;\n\n      let delay=speed;\n\n      if(char===\".\"){delay=speed*5;}\n      if(char===\",\"){delay=speed*2.5;}\n      if(char===\"\\n\"){delay=speed*4;}\n\n      setTimeout(typing,delay);\n    }else{\n      if(callback){callback();}\n    }\n  }\n\n  typing();\n}\n\nfunction switchScene(currentScene,nextScene,callback){\n  currentScene.classList.add(\"fade-out\");\n\n  setTimeout(function(){\n    currentScene.classList.remove(\"active\");\n    currentScene.classList.remove(\"fade-out\");\n    nextScene.classList.add(\"active\");\n\n    if(callback){callback();}\n  },850);\n}\n\nfunction fitVideoScreen(){\n  const baseWidth=1180;\n  const baseHeight=664;\n  const safePadding=24;\n  const availableWidth=window.innerWidth-safePadding;\n  const availableHeight=window.innerHeight-safePadding;\n  const scaleByWidth=availableWidth\/baseWidth;\n  const scaleByHeight=availableHeight\/baseHeight;\n  const finalScale=Math.min(scaleByWidth,scaleByHeight,1);\n  document.documentElement.style.setProperty(\"--ols-video-screen-scale\",finalScale.toFixed(4));\n}\n\nfunction fitMcqScreen(){\n  const baseWidth=1360;\n  const baseHeight=1130;\n  const safePadding=24;\n  const availableWidth=window.innerWidth-safePadding;\n  const availableHeight=window.innerHeight-safePadding;\n  const scaleByWidth=availableWidth\/baseWidth;\n  const scaleByHeight=availableHeight\/baseHeight;\n  const finalScale=Math.min(scaleByWidth,scaleByHeight,1);\n  document.documentElement.style.setProperty(\"--ols-mcq-screen-scale\",finalScale.toFixed(4));\n}\n\nfunction fitSaqScreen(){\n  const baseWidth=1360;\n  const baseHeight=965;\n  const safePadding=24;\n  const availableWidth=window.innerWidth-safePadding;\n  const availableHeight=window.innerHeight-safePadding;\n  const scaleByWidth=availableWidth\/baseWidth;\n  const scaleByHeight=availableHeight\/baseHeight;\n  const finalScale=Math.min(scaleByWidth,scaleByHeight,1);\n  document.documentElement.style.setProperty(\"--ols-saq-screen-scale\",finalScale.toFixed(4));\n}\n\nfunction fitAllScreens(){\n  fitVideoScreen();\n  fitMcqScreen();\n  fitSaqScreen();\n}\n\nwindow.addEventListener(\"resize\",fitAllScreens);\nwindow.addEventListener(\"orientationchange\",fitAllScreens);\nfitAllScreens();\n\nconst sceneVideo=document.getElementById(\"sceneVideo\");\nconst sceneMcq=document.getElementById(\"sceneMcq\");\nconst sceneSaq=document.getElementById(\"sceneSaq\");\n\nconst videoTitle=\"Online Chemistry Lessons\";\nconst videoTitleText=document.getElementById(\"videoTitleText\");\nconst videoTitleCursor=document.getElementById(\"videoTitleCursor\");\nconst videoTitleScreen=document.getElementById(\"videoTitleScreen\");\nconst videoScene=document.getElementById(\"videoScene\");\nconst lessonVideo=document.getElementById(\"lessonVideo\");\n\nlet videoFallbackTimer=null;\nlet videoSceneComplete=false;\n\nfunction playLessonVideo(){\n  lessonVideo.muted=true;\n  lessonVideo.currentTime=0;\n\n  const playPromise=lessonVideo.play();\n\n  if(playPromise!==undefined){\n    playPromise.catch(function(){\n      lessonVideo.muted=true;\n    });\n  }\n}\n\nfunction completeVideoScene(){\n  if(videoSceneComplete){return;}\n\n  videoSceneComplete=true;\n\n  if(videoFallbackTimer){\n    clearTimeout(videoFallbackTimer);\n  }\n\n  lessonVideo.pause();\n\n  setTimeout(function(){\n    switchScene(sceneVideo,sceneMcq,function(){\n      startMcqIntro();\n    });\n  },1400);\n}\n\nlessonVideo.addEventListener(\"ended\",function(){\n  lessonVideo.pause();\n  completeVideoScene();\n});\n\nfunction startVideoSection(){\n  fitVideoScreen();\n\n  setTimeout(function(){\n    typeWriter(videoTitleText,videoTitle,44,function(){\n      setTimeout(function(){\n        videoTitleCursor.style.display=\"none\";\n\n        setTimeout(function(){\n          videoTitleScreen.classList.add(\"hide\");\n\n          setTimeout(function(){\n            videoScene.classList.add(\"show\");\n\n            setTimeout(function(){\n              playLessonVideo();\n\n              videoFallbackTimer=setTimeout(function(){\n                completeVideoScene();\n              },45000);\n            },600);\n          },850);\n        },3000);\n      },250);\n    });\n  },700);\n}\n\nconst mcqIntroTitle=\"Multiple Choice Question Bank\";\nconst mcqSpecificFeedbackText=\"XF would suggest that X forms a 1+ ion, but the large jump after the second ionisation energy shows that two outer electrons are removed before reaching an inner shell.\";\nconst mcqGeneralFeedbackText=\n\"Your answer is incorrect.\\n\\n\"+\n\"To identify the likely ion formed by element X, look for the large jump in successive ionisation energies.\\n\\n\"+\n\"\u2022 The first and second electrons are removed relatively easily.\\n\"+\n\"\u2022 The third ionisation energy is much larger, showing that the third electron is removed from an inner shell.\\n\"+\n\"\u2022 Therefore, element X has two outer-shell electrons.\\n\"+\n\"\u2022 It is most likely a Group 2 element and forms X\u00b2\u207a ions.\\n\\n\"+\n\"Fluoride ions are F\u207b, so two fluoride ions are needed to balance one X\u00b2\u207a ion.\\n\\n\"+\n\"The correct answer is: XF\u2082\";\n\nconst mcqIntroScreen=document.getElementById(\"mcqIntroScreen\");\nconst mcqIntroTitleText=document.getElementById(\"mcqIntroTitleText\");\nconst mcqIntroTitleCursor=document.getElementById(\"mcqIntroTitleCursor\");\nconst mcqScreen=document.getElementById(\"mcqScreen\");\nconst mcqWrongOption=document.getElementById(\"mcqWrongOption\");\nconst mcqSubmitButton=document.getElementById(\"mcqSubmitButton\");\nconst mcqSpecificFeedback=document.getElementById(\"mcqSpecificFeedback\");\nconst mcqCrossIcon=document.getElementById(\"mcqCrossIcon\");\nconst mcqSpecificText=document.getElementById(\"mcqSpecificText\");\nconst mcqSpecificCursor=document.getElementById(\"mcqSpecificCursor\");\nconst mcqGeneralFeedback=document.getElementById(\"mcqGeneralFeedback\");\nconst mcqGeneralText=document.getElementById(\"mcqGeneralText\");\nconst mcqGeneralCursor=document.getElementById(\"mcqGeneralCursor\");\n\nfunction selectMcqWrongOption(){\n  mcqWrongOption.classList.add(\"clicking\");\n\n  setTimeout(function(){\n    mcqWrongOption.classList.add(\"selected\");\n  },220);\n\n  setTimeout(function(){\n    mcqWrongOption.classList.remove(\"clicking\");\n  },850);\n}\n\nfunction clickMcqSubmit(){\n  mcqSubmitButton.classList.add(\"clicked\");\n\n  setTimeout(function(){\n    mcqSubmitButton.classList.remove(\"clicked\");\n  },240);\n}\n\nfunction showMcqSpecificFeedback(){\n  mcqSpecificFeedback.classList.add(\"show\");\n\n  setTimeout(function(){\n    mcqCrossIcon.classList.add(\"show\");\n  },180);\n\n  setTimeout(function(){\n    mcqSpecificCursor.style.display=\"inline-block\";\n\n    typeWriter(mcqSpecificText,mcqSpecificFeedbackText,12,function(){\n      mcqSpecificCursor.style.display=\"none\";\n\n      setTimeout(function(){\n        showMcqGeneralFeedback();\n      },650);\n    });\n  },560);\n}\n\nfunction showMcqGeneralFeedback(){\n  mcqGeneralFeedback.classList.add(\"show\");\n\n  setTimeout(function(){\n    mcqGeneralCursor.style.display=\"inline-block\";\n\n    typeWriter(mcqGeneralText,mcqGeneralFeedbackText,8,function(){\n      mcqGeneralCursor.style.display=\"none\";\n\n      setTimeout(function(){\n        switchScene(sceneMcq,sceneSaq,function(){\n          startSaqIntro();\n        });\n      },2600);\n    });\n  },600);\n}\n\nfunction startMcqAnimation(){\n  fitMcqScreen();\n  mcqScreen.classList.add(\"show\");\n\n  setTimeout(function(){\n    selectMcqWrongOption();\n\n    setTimeout(function(){\n      clickMcqSubmit();\n\n      setTimeout(function(){\n        showMcqSpecificFeedback();\n      },620);\n    },1150);\n  },1300);\n}\n\nfunction startMcqIntro(){\n  fitMcqScreen();\n\n  setTimeout(function(){\n    typeWriter(mcqIntroTitleText,mcqIntroTitle,44,function(){\n      setTimeout(function(){\n        mcqIntroTitleCursor.style.display=\"none\";\n\n        setTimeout(function(){\n          mcqIntroScreen.classList.add(\"hide\");\n\n          setTimeout(function(){\n            startMcqAnimation();\n          },850);\n        },3000);\n      },250);\n    });\n  },700);\n}\n\nconst saqIntroTitle=\"Chemistry Specialist\\nMarked Exam Feedback\";\nconst saqStudentAnswer=\"First ionisation energy increases because the atoms get heavier and have more electrons across the period.\";\nconst saqTeacherFeedbackText=\n\"Comment:\\n\"+\n\"This answer is not specific enough. Atomic mass is not the main reason why first ionisation energy increases across a period.\\n\\n\"+\n\"Across Period 3, the number of protons increases, so nuclear charge increases. Each extra electron is added to the same principal shell, so shielding is similar. The stronger attraction from the nucleus pulls the outer electrons closer, decreasing atomic radius.\\n\\n\"+\n\"Because the outer electron is closer to the nucleus and more strongly attracted, more energy is needed to remove it. This explains the general increase in first ionisation energy across the period.\\n\\n\"+\n\"Next time, include:\\n\"+\n\"\u2022 Nuclear charge increases across the period \u2713\\n\"+\n\"\u2022 Shielding remains similar because electrons are added to the same shell \u2713\\n\"+\n\"\u2022 Atomic radius decreases, so attraction to the outer electron increases \u2713\\n\"+\n\"\u2022 More energy is needed to remove the outer electron \u2713\\n\\n\"+\n\"You were close to discussing periodic trends, but the explanation must use nuclear charge, shielding and distance from the nucleus.\";\n\nconst saqIntro=document.getElementById(\"saqIntro\");\nconst saqIntroTitleText=document.getElementById(\"saqIntroTitleText\");\nconst saqIntroTitleCursor=document.getElementById(\"saqIntroTitleCursor\");\nconst saqStudentText=document.getElementById(\"saqStudentText\");\nconst saqTeacherText=document.getElementById(\"saqTeacherText\");\nconst saqStudentCursor=document.getElementById(\"saqStudentCursor\");\nconst saqTeacherCursor=document.getElementById(\"saqTeacherCursor\");\nconst saqFeedbackBox=document.getElementById(\"saqTeacherFeedback\");\nconst saqScreen=document.getElementById(\"saqScreen\");\n\nfunction startSaqFeedbackAnimation(){\n  fitSaqScreen();\n  saqScreen.classList.add(\"show\");\n\n  setTimeout(function(){\n    typeWriter(saqStudentText,saqStudentAnswer,27,function(){\n      saqStudentCursor.style.display=\"none\";\n\n      setTimeout(function(){\n        saqFeedbackBox.classList.add(\"show\");\n        saqTeacherCursor.style.display=\"inline-block\";\n\n        typeWriter(saqTeacherText,saqTeacherFeedbackText,10,function(){\n          saqTeacherCursor.style.display=\"none\";\n        });\n      },650);\n    });\n  },850);\n}\n\nfunction startSaqIntro(){\n  fitSaqScreen();\n\n  setTimeout(function(){\n    typeWriter(saqIntroTitleText,saqIntroTitle,44,function(){\n      setTimeout(function(){\n        saqIntroTitleCursor.style.display=\"none\";\n\n        setTimeout(function(){\n          saqIntro.classList.add(\"hide\");\n\n          setTimeout(function(){\n            startSaqFeedbackAnimation();\n          },850);\n        },3000);\n      },250);\n    });\n  },700);\n}\n\nstartVideoSection();\n<\/script>\n<\/body>\n<\/html>\n  <\/template>\n\n  <script>\n    (function(){\n      var startButton = document.getElementById(\"olsCourseAnimationStart002\");\n      var pauseButton = document.getElementById(\"olsCourseAnimationPause002\");\n      var iframe = document.getElementById(\"olsCourseAnimationFrame002\");\n      var template = document.getElementById(\"olsCourseAnimationTemplate002\");\n\n      if (!startButton || !pauseButton || !iframe || !template) {\n        return;\n      }\n\n      startButton.addEventListener(\"click\", function(){\n        iframe.setAttribute(\"srcdoc\", template.innerHTML);\n        startButton.classList.add(\"is-hidden\");\n        pauseButton.classList.add(\"is-visible\");\n        pauseButton.textContent = \"Pause\";\n        pauseButton.setAttribute(\"aria-label\", \"Pause course preview animation\");\n      });\n\n      pauseButton.addEventListener(\"click\", function(){\n        if (!iframe.contentWindow || typeof iframe.contentWindow.olsToggleAnimationPause !== \"function\") {\n          return;\n        }\n\n        var state = iframe.contentWindow.olsToggleAnimationPause();\n\n        if (state === \"paused\") {\n          pauseButton.textContent = \"Resume\";\n          pauseButton.setAttribute(\"aria-label\", \"Resume course preview animation\");\n        } else {\n          pauseButton.textContent = \"Pause\";\n          pauseButton.setAttribute(\"aria-label\", \"Pause course preview animation\");\n        }\n      });\n    })();\n  <\/script>\n<\/section>\n\n      <section class=\"ols-faq-card\">\n        <h2>FAQs<\/h2>\n        <p>These questions focus on the main exam points for identifying compounds from mass spectra.<\/p>\n\n        <div class=\"ols-faq-list\">\n          <div class=\"ols-faq-item\">\n            <h3>What is the molecular ion peak?<\/h3>\n            <p>The molecular ion peak is the peak caused by the whole molecule after it has lost one electron. It is often written as the M<sup>+<\/sup> peak.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>How does the molecular ion peak identify molecular mass?<\/h3>\n            <p>If the molecular ion has a 1+ charge, the m\/z value of the molecular ion peak is equal to the relative molecular mass of the compound.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why might there be a small peak after the M<sup>+<\/sup> peak?<\/h3>\n            <p>A small M+1 peak can occur because of naturally occurring heavier isotopes, such as carbon-13. This should not normally be used as the main molecular ion peak.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why is ethanol identified from a molecular ion peak at m\/z 46?<\/h3>\n            <p>Ethanol has formula C<sub>2<\/sub>H<sub>5<\/sub>OH. Its relative molecular mass is (2 &times; 12.0) + (6 &times; 1.0) + 16.0 = 46.0, matching the molecular ion peak at m\/z 46.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Are fragment peaks useful for identification?<\/h3>\n            <p>Yes. Fragment peaks help support the proposed structure because different compounds can break into different characteristic ions.<\/p>\n          <\/div>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-related-card\">\n        <h2>Related Topics<\/h2>\n        <p>Use these related pages to strengthen your understanding of mass spectrometry and isotope analysis.<\/p>\n\n        <div class=\"ols-related-grid\">\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/the-mass-spectrometer\/\">The Mass Spectrometer<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/ram-calculations\/\">RAM Calculations<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/predicting-diatomic-mass-spectra\/\">Predicting Diatomic Mass Spectra<\/a>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-attribution-card\">\n        <p><strong>Copyright notice:<\/strong> This revision page and its explanations are original OLS teaching resources written for Online Learning System by <strong>Dr. Mohammed Al-Fatah<\/strong>. They are provided for student revision and may not be copied, republished or redistributed without permission.<\/p>\n      <\/section>\n\n      <!-- OLS Author Copyright Footprint \/ Attribution Card -->\n      <section class=\"ols-attribution-card\">\n        <style>\n          .ols-attribution-card {\n            background: linear-gradient(135deg, #ffffff, #f8fbff);\n            border: 1px solid rgba(28, 36, 75, 0.14);\n            border-radius: 28px;\n            box-shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n            padding: 34px;\n            margin-bottom: 24px;\n            overflow: hidden;\n            font-family: Poppins, Arial, sans-serif;\n            box-sizing: border-box;\n          }\n      \n          .ols-attribution-card,\n          .ols-attribution-card * {\n            box-sizing: border-box;\n          }\n      \n          .ols-attribution-card p {\n            margin: 0;\n            font-size: 14px;\n            line-height: 1.65;\n            font-weight: 300;\n            color: #667085;\n          }\n      \n          .ols-attribution-card strong {\n            font-weight: 700;\n            color: #1C244B;\n          }\n      \n          @media (max-width: 760px) {\n            .ols-attribution-card {\n              padding: 24px 18px;\n              border-radius: 22px;\n            }\n          }\n        <\/style>\n      \n        <p><strong>Copyright notice:<\/strong> This OLS revision content, including the explanations, layout, diagrams, tables and embedded learning structure, is authored for Online Learning System by Dr. Mohammed Al-Fatah. It may not be copied, reproduced, redistributed or adapted without written permission.<\/p>\n      <\/section>\n    <\/main>\n\n  <script type=\"application\/ld+json\">\n  {\n    \"@context\": \"https:\/\/schema.org\",\n    \"@graph\": [\n      {\n        \"@type\": \"WebPage\",\n        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/identifying-compounds-from-mass-spectra\/#webpage\",\n        \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/identifying-compounds-from-mass-spectra\/\",\n        \"name\": \"Identifying Compounds from Mass Spectra\",\n        \"description\": \"A Level Chemistry revision notes explaining how to use the molecular ion peak and mass spectrum peak pattern to identify unknown compounds, including ethanol at m\/z 46.\",\n        \"isPartOf\": {\n          \"@type\": \"WebSite\",\n          \"name\": \"Online Learning System\",\n          \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/\"\n        },\n        \"about\": [\n          { \"@type\": \"Thing\", \"name\": \"Mass spectrometry\" },\n          { \"@type\": \"Thing\", \"name\": \"Molecular ion peak\" },\n          { \"@type\": \"Thing\", \"name\": \"Identifying unknown compounds\" }\n        ],\n        \"educationalLevel\": \"A Level\",\n        \"inLanguage\": \"en-GB\"\n      },\n      {\n        \"@type\": \"BreadcrumbList\",\n        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/identifying-compounds-from-mass-spectra\/#breadcrumb\",\n        \"itemListElement\": [\n          {\n            \"@type\": \"ListItem\",\n            \"position\": 1,\n            \"name\": \"Revision Notes\",\n            \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\"\n          },\n          {\n            \"@type\": \"ListItem\",\n            \"position\": 2,\n            \"name\": \"A Level Chemistry\",\n            \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\"\n          },\n          {\n            \"@type\": \"ListItem\",\n            \"position\": 3,\n            \"name\": \"Edexcel International\",\n            \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\"\n          },\n          {\n            \"@type\": \"ListItem\",\n            \"position\": 4,\n            \"name\": \"Topic 2 Atomic Structure and The Periodic Table\",\n            \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/\"\n          },\n          {\n            \"@type\": \"ListItem\",\n            \"position\": 5,\n            \"name\": \"Mass Spectrometry\",\n            \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/\"\n          },\n          {\n            \"@type\": \"ListItem\",\n            \"position\": 6,\n            \"name\": \"Identifying Compounds from Mass Spectra\",\n            \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/identifying-compounds-from-mass-spectra\/\"\n          }\n        ]\n      },\n      {\n        \"@type\": \"Course\",\n        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/atomic-structure-and-periodic-table-edexcel-t2\/#course\",\n        \"name\": \"Edexcel International A Level Chemistry Topic 2 Atomic Structure and The Periodic Table\",\n        \"description\": \"A complete OLS course covering atomic structure, isotopes, mass spectrometry, ionisation energy, electron configuration and periodic trends for Edexcel International A Level Chemistry.\",\n        \"provider\": {\n          \"@type\": \"Organization\",\n          \"name\": \"Online Learning System\",\n          \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/\"\n        },\n        \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/atomic-structure-and-periodic-table-edexcel-t2\/\"\n      },\n      {\n        \"@type\": \"FAQPage\",\n        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/identifying-compounds-from-mass-spectra\/#faq\",\n        \"mainEntity\": [\n          {\n            \"@type\": \"Question\",\n            \"name\": \"What is the molecular ion peak?\",\n            \"acceptedAnswer\": {\n              \"@type\": \"Answer\",\n              \"text\": \"The molecular ion peak is the peak caused by the whole molecule after it has lost one electron. It is often written as the M+ peak.\"\n            }\n          },\n          {\n            \"@type\": \"Question\",\n            \"name\": \"How does the molecular ion peak identify molecular mass?\",\n            \"acceptedAnswer\": {\n              \"@type\": \"Answer\",\n              \"text\": \"If the molecular ion has a 1+ charge, the m\/z value of the molecular ion peak is equal to the relative molecular mass of the compound.\"\n            }\n          },\n          {\n            \"@type\": \"Question\",\n            \"name\": \"Why might there be a small peak after the M+ peak?\",\n            \"acceptedAnswer\": {\n              \"@type\": \"Answer\",\n              \"text\": \"A small M+1 peak can occur because of naturally occurring heavier isotopes, such as carbon-13. This should not normally be used as the main molecular ion peak.\"\n            }\n          },\n          {\n            \"@type\": \"Question\",\n            \"name\": \"Why is ethanol identified from a molecular ion peak at m\/z 46?\",\n            \"acceptedAnswer\": {\n              \"@type\": \"Answer\",\n              \"text\": \"Ethanol has formula C2H5OH. Its relative molecular mass is 46.0, matching the molecular ion peak at m\/z 46.\"\n            }\n          },\n          {\n            \"@type\": \"Question\",\n            \"name\": \"Are fragment peaks useful for identification?\",\n            \"acceptedAnswer\": {\n              \"@type\": \"Answer\",\n              \"text\": \"Yes. Fragment peaks help support the proposed structure because different compounds can break into different characteristic ions.\"\n            }\n          }\n        ]\n      }\n    ]\n  }\n  <\/script>\n<\/section>\n\n","protected":false},"excerpt":{"rendered":"<p>Revision Notes \/ A Level Chemistry \/ Edexcel International \/ Topic 2 Atomic Structure &amp; The Periodic Table \/ Mass Spectrometry \/ Identifying Compounds from Mass Spectra Identifying Compounds from Mass Spectra A concise revision guide to using the molecular ion peak and peak pattern in a mass spectrum to help identify an unknown compound. [&hellip;]<\/p>\n","protected":false},"author":12,"featured_media":0,"parent":3987,"menu_order":3,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-3993","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/3993","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/comments?post=3993"}],"version-history":[{"count":0,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/3993\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/3987"}],"wp:attachment":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/media?parent=3993"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}