{"id":4519,"date":"2026-05-28T06:05:13","date_gmt":"2026-05-28T05:05:13","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-atomic-structure-and-the-periodic-table\/mass-spectrometry\/ram-calculations\/"},"modified":"2026-05-30T07:45:15","modified_gmt":"2026-05-30T06:45:15","slug":"ram-calculations","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-atomic-structure-and-the-periodic-table\/mass-spectrometry\/ram-calculations\/","title":{"rendered":"RAM Calculations"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-ram-calculations-9ch0-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    .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      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-direction: column;\n      align-items: flex-start;\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      transition: transform 0.25s ease, box-shadow 0.25s ease;\n    }\n\n    .ols-author:hover .ols-author-avatar-img {\n      transform: scale(1.04);\n      box-shadow: 0 20px 42px rgba(28,36,75,0.22), 0 0 0 1px rgba(28,36,75,0.10);\n    }\n\n    .ols-author-content { min-width: 0; }\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      letter-spacing: 0.01em;\n      box-shadow: 0 10px 22px rgba(10,102,194,0.24);\n      position: relative;\n      overflow: hidden;\n      transition: transform 0.22s ease, box-shadow 0.22s ease;\n    }\n\n    .ols-linkedin-pill::before {\n      content: \"\";\n      position: absolute;\n      top: 0;\n      left: -120%;\n      width: 100%;\n      height: 100%;\n      background: linear-gradient(120deg, rgba(255,255,255,0) 0%, rgba(255,255,255,0.28) 50%, rgba(255,255,255,0) 100%);\n      transition: left 0.7s 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-pill:hover::before { left: 120%; }\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 {\n      font-weight: 700;\n      color: var(--navy);\n    }\n\n    .ols-note-card ul,\n    .ols-note-card ol {\n      margin: 0;\n      padding-left: 22px;\n    }\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-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      display: grid;\n      gap: 14px;\n      margin-top: 18px;\n    }\n\n    .ols-rule-item {\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      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      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-worked-grid {\n      display: grid;\n      gap: 14px;\n      margin-top: 20px;\n    }\n\n    .ols-worked-step {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 18px;\n      box-shadow: var(--inner-shadow);\n    }\n\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-worked-step p {\n      margin: 0;\n      font-size: 16px;\n      line-height: 1.65;\n    }\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,\n    .ols-course-cta * { box-sizing: border-box; }\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: 34px;\n      text-align: center;\n    }\n\n    .ols-course-cta-pill {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      padding: 8px 14px;\n      border-radius: 999px;\n      background: rgba(37, 99, 235, 0.10);\n      color: var(--blue);\n      border: 1px solid rgba(37, 99, 235, 0.18);\n      font-size: 13px;\n      font-weight: 700;\n      margin-bottom: 14px;\n    }\n\n    .ols-course-cta-card h2 {\n      margin: 0 0 12px;\n      font-size: clamp(30px, 4vw, 46px);\n      line-height: 1.15;\n      font-weight: 800;\n      color: #111827;\n      letter-spacing: -0.03em;\n    }\n\n    .ols-course-cta-card p {\n      margin: 0 auto 22px;\n      max-width: 750px;\n      font-size: 18px;\n      line-height: 1.65;\n      font-weight: 300;\n      color: var(--body-text);\n    }\n\n    .ols-cta-button {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      padding: 14px 26px;\n      border-radius: 999px;\n      background: var(--navy);\n      color: #ffffff;\n      text-decoration: none;\n      font-weight: 700;\n      box-shadow: 0 12px 26px rgba(28,36,75,0.18);\n      transition: transform 0.2s ease, box-shadow 0.2s ease;\n    }\n\n    .ols-cta-button:hover {\n      transform: translateY(-2px);\n      box-shadow: 0 16px 34px rgba(28,36,75,0.22);\n      color: #ffffff;\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      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 * { box-sizing: border-box; }\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      .ols-main { max-width: none; }\n      .ols-related-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }\n    }\n\n    @media (max-width: 760px) {\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      .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 {\n        border-collapse: separate;\n        border-spacing: 0;\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\n      .ols-snap-item {\n        grid-template-columns: 1fr;\n      }\n    }\n\n    .ols-zoom-card, .ols-zoom-card * { box-sizing: border-box; }\n    .ols-zoom-card { display: block !important; margin: 26px 0 34px !important; border: 1px solid rgba(28, 36, 75, 0.14) !important; border-radius: 26px !important; background: #ffffff !important; box-shadow: 0 18px 45px rgba(28, 36, 75, 0.10) !important; overflow: visible !important; position: relative !important; z-index: 1 !important; isolation: isolate !important; }\n    .ols-zoom-card:hover { z-index: 50 !important; }\n    .ols-zoom-card-image { display: flex !important; align-items: center !important; justify-content: center !important; width: 100% !important; min-height: 330px !important; padding: 20px !important; background: #ffffff !important; overflow: visible !important; border-top-left-radius: 26px !important; border-top-right-radius: 26px !important; position: relative !important; z-index: 2 !important; }\n    .ols-zoom-card img.ols-zoomable-img { display: block !important; width: 100% !important; max-width: 100% !important; height: auto !important; border-radius: 18px !important; cursor: default !important; pointer-events: auto !important; user-select: none !important; -webkit-user-drag: none !important; transform: translateZ(0) scale(1) !important; transform-origin: center center !important; transition: transform 0.32s ease, box-shadow 0.32s ease, filter 0.32s ease !important; position: relative !important; z-index: 2 !important; }\n    @media (hover: hover) and (pointer: fine) { .ols-zoom-card img.ols-zoomable-img:hover { transform: translateZ(0) scale(1.45) !important; box-shadow: 0 28px 70px rgba(28, 36, 75, 0.34) !important; filter: saturate(1.02) contrast(1.01) !important; z-index: 100 !important; } }\n    .ols-zoom-card-caption { padding: 18px 22px 20px !important; background: linear-gradient(135deg, #ffffff, #f8fbff) !important; border-bottom-left-radius: 26px !important; border-bottom-right-radius: 26px !important; position: relative !important; z-index: 1 !important; }\n    .ols-zoom-card-caption p { margin: 0 !important; color: #5f6b85 !important; font-size: 15px !important; line-height: 1.65 !important; font-weight: 300 !important; font-style: italic !important; font-family: Poppins, Arial, sans-serif !important; }\n    .ols-zoom-card img.ols-lightbox-target { cursor: zoom-in !important; }\n    @media (max-width: 760px) { .ols-zoom-card { border-radius: 22px !important; overflow: hidden !important; } .ols-zoom-card-image { min-height: auto !important; padding: 12px !important; overflow: hidden !important; } .ols-zoom-card img.ols-zoomable-img, .ols-zoom-card img.ols-zoomable-img:hover { transform: none !important; box-shadow: none !important; } }\n    .ols-image-lightbox { position: fixed; inset: 0; z-index: 999999; display: none; align-items: center; justify-content: center; padding: 34px; background: rgba(10, 15, 35, 0.86); backdrop-filter: blur(8px); -webkit-backdrop-filter: blur(8px); }\n    .ols-image-lightbox.is-open { display: flex; }\n    .ols-image-lightbox-inner { position: relative; width: min(96vw, 1500px); max-height: 92vh; display: flex; align-items: center; justify-content: center; }\n    .ols-image-lightbox-img { display: block; max-width: 100%; max-height: 92vh; height: auto; width: auto; border-radius: 22px; background: #ffffff; box-shadow: 0 32px 90px rgba(0,0,0,0.45); object-fit: contain; }\n    .ols-image-lightbox-close { position: absolute; top: -18px; right: -18px; width: 46px; height: 46px; border: 0; border-radius: 50%; background: #ffffff; color: #1C244B; font-family: Poppins, Arial, sans-serif; font-size: 28px; line-height: 1; font-weight: 700; cursor: pointer; box-shadow: 0 16px 34px rgba(0,0,0,0.28); display: flex; align-items: center; justify-content: center; transition: transform 0.2s ease, background 0.2s ease, color 0.2s ease; }\n    .ols-image-lightbox-close:hover { transform: scale(1.08); background: #2563eb; color: #ffffff; }\n    @media (max-width: 760px) { .ols-image-lightbox { padding: 16px; } .ols-image-lightbox-inner { width: 100%; max-height: 88vh; } .ols-image-lightbox-img { max-height: 88vh; border-radius: 16px; } .ols-image-lightbox-close { top: 10px; right: 10px; width: 42px; height: 42px; font-size: 26px; } }\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 1 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\/topic-1-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\/topic-1-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\/topic-1-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\/topic-1-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\/topic-1-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\/topic-1-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\/topic-1-atomic-structure-and-the-periodic-table\/electron-configuration\/\">Electron Configuration<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-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\/topic-1-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\/topic-1-atomic-structure-and-the-periodic-table\/ionisation-energy\/successive-ionisation-energies\/\">Successive Ionisation Energies<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-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\/topic-1-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\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-atomic-structure-and-the-periodic-table\/periodic-trends\/\">Periodic Trends<\/a>\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\/topic-2-bonding-and-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\/topic-3-redox-i\/\">Redox I<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/\">Inorganic Chemistry &amp; The Periodic Table<\/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>\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\/\">Edexcel<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-atomic-structure-and-the-periodic-table\/\">Topic 1 Atomic Structure &amp; The Periodic Table<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-atomic-structure-and-the-periodic-table\/mass-spectrometry\/\">Mass Spectrometry<\/a> \/\n        <span>RAM Calculations<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>RAM Calculations<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to calculating relative atomic mass from isotopic abundances, mass spectra and missing isotope data.<\/p>\n\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Unit: Paper 1<\/div>\n          <div class=\"ols-badge\">Topic 1: Atomic Structure &amp; The Periodic Table<\/div>\n          <div class=\"ols-badge\">9CH0\/01<\/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        <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        View LinkedIn Profile\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 Relative Atomic Mass Means<\/h2><\/div>\n        <p><strong>Relative atomic mass<\/strong>, A<sub>r<\/sub>, is the weighted mean mass of an atom of an element compared with one twelfth of the mass of a carbon-12 atom.<\/p>\n        <p>Most elements exist as a mixture of isotopes. This means the relative atomic mass is usually not a whole number, because it depends on both the <strong>relative isotopic masses<\/strong> and the <strong>relative abundances<\/strong> of those isotopes.<\/p>\n        <div class=\"ols-key-box\"><p><strong>Key idea:<\/strong> the isotope that is more abundant has a greater effect on the final A<sub>r<\/sub> value.<\/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>The Relative Atomic Mass Formula<\/h2><\/div>\n        <p>To calculate A<sub>r<\/sub>, multiply each isotopic mass by its abundance, add the results, then divide by the total abundance.<\/p>\n\n        <div class=\"ols-formula-box\">\n          <p>A<sub>r<\/sub> = \u03a3(isotopic mass \u00d7 abundance) \u00f7 \u03a3(abundance)<\/p>\n          <small>If percentage abundances are used, the total abundance is usually 100.<\/small>\n        <\/div>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Data type<\/th>\n                <th>How to divide<\/th>\n                <th>Typical exam wording<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Data type\">Percentage abundance<\/td>\n                <td data-label=\"How to divide\">Divide by 100<\/td>\n                <td data-label=\"Typical exam wording\">20.0% of atoms are boron-10 and 80.0% are boron-11<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Data type\">Relative abundance from a mass spectrum<\/td>\n                <td data-label=\"How to divide\">Divide by the sum of the peak abundances<\/td>\n                <td data-label=\"Typical exam wording\">The peaks have relative abundances of 114.0, 0.2 and 11.2<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n      <\/article>\n\n      <div class=\"ols-zoom-card\">\n        <div class=\"ols-zoom-card-image\">\n          <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Calculating-relative-atomic-mass-tutorial.webp\" alt=\"Worked tutorial showing how to calculate relative atomic mass from mass spectrum peak abundances\" class=\"ols-zoomable-img ols-lightbox-target\" draggable=\"false\">\n        <\/div>\n        <div class=\"ols-zoom-card-caption\">\n          <p>Mass spectrum peak heights act as relative abundances, so they must be included in the weighted mean calculation.<\/p>\n        <\/div>\n      <\/div>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">3<\/div><h2>Calculating A<sub>r<\/sub> from Isotopic Abundances<\/h2><\/div>\n        <p>When the abundances are percentages, the calculation is straightforward because the total abundance is 100.<\/p>\n\n        <div class=\"ols-worked-grid\">\n          <div class=\"ols-worked-step\">\n            <h3>Example: boron<\/h3>\n            <p>20.0% of boron atoms have relative isotopic mass 10.0 and 80.0% have relative isotopic mass 11.0.<\/p>\n          <\/div>\n          <div class=\"ols-worked-step\">\n            <h3>Step 1: multiply and add<\/h3>\n            <p>(20.0 \u00d7 10.0) + (80.0 \u00d7 11.0) = 200.0 + 880.0 = 1080.0<\/p>\n          <\/div>\n          <div class=\"ols-worked-step\">\n            <h3>Step 2: divide by 100<\/h3>\n            <p>1080.0 \u00f7 100 = <strong>10.8<\/strong><\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\"><p><strong>Exam focus:<\/strong> do not simply average 10.0 and 11.0. The answer is closer to 11.0 because boron-11 is more abundant.<\/p><\/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>Calculating A<sub>r<\/sub> from a Mass Spectrum<\/h2><\/div>\n        <p>In a simple isotope mass spectrum, the <strong>x-axis<\/strong> gives the m\/z values. If the ions have a 1+ charge, these m\/z values can usually be treated as the relative isotopic masses.<\/p>\n        <p>The <strong>height of each peak<\/strong> shows the relative abundance of that isotope. Use these peak heights in the weighted mean calculation.<\/p>\n\n        <div class=\"ols-worked-grid\">\n          <div class=\"ols-worked-step\">\n            <h3>Example: chlorine<\/h3>\n            <p>Chlorine has peaks at m\/z 35 and m\/z 37 with abundances of 75.5% and 24.5%.<\/p>\n          <\/div>\n          <div class=\"ols-worked-step\">\n            <h3>Calculation<\/h3>\n            <p>A<sub>r<\/sub> = [(35 \u00d7 75.5) + (37 \u00d7 24.5)] \u00f7 100 = 35.49, so A<sub>r<\/sub> \u2248 <strong>35.5<\/strong>.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <div class=\"ols-zoom-card\">\n        <div class=\"ols-zoom-card-image\">\n          <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Mass-spectra-of-chlorine-isotopes.webp\" alt=\"Mass spectrum of chlorine showing peaks for chlorine-35 and chlorine-37 isotopes\" class=\"ols-zoomable-img ols-lightbox-target\" draggable=\"false\">\n        <\/div>\n        <div class=\"ols-zoom-card-caption\">\n          <p>The two chlorine peaks show that chlorine-35 is more abundant than chlorine-37, so the A<sub>r<\/sub> is closer to 35 than 37.<\/p>\n        <\/div>\n      <\/div>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">5<\/div><h2>When Abundances Are Not Percentages<\/h2><\/div>\n        <p>Some questions give relative abundances that do not add up to 100. In these cases, divide by the <strong>sum of the relative abundances<\/strong>, not by 100.<\/p>\n\n        <div class=\"ols-worked-grid\">\n          <div class=\"ols-worked-step\">\n            <h3>Example: neon spectrum<\/h3>\n            <p>Masses 20, 21 and 22 have relative abundances of 114.0, 0.2 and 11.2.<\/p>\n          <\/div>\n          <div class=\"ols-worked-step\">\n            <h3>Step 1: multiply and add<\/h3>\n            <p>(20 \u00d7 114.0) + (21 \u00d7 0.2) + (22 \u00d7 11.2) = 2530.6<\/p>\n          <\/div>\n          <div class=\"ols-worked-step\">\n            <h3>Step 2: divide by total abundance<\/h3>\n            <p>Total abundance = 114.0 + 0.2 + 11.2 = 125.4<\/p>\n            <p>2530.6 \u00f7 125.4 = <strong>20.2<\/strong><\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\"><p><strong>Common mistake:<\/strong> only divide by 100 when the abundances are percentages that total 100.<\/p><\/div>\n      <\/article>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">6<\/div><h2>Finding Missing Isotope Data<\/h2><\/div>\n        <p>Some questions give the A<sub>r<\/sub> and some isotope data, then ask for the abundance or isotopic mass of a missing isotope. Use the same weighted mean equation, but rearrange it.<\/p>\n\n        <div class=\"ols-worked-grid\">\n          <div class=\"ols-worked-step\">\n            <h3>Example: silicon abundance<\/h3>\n            <p>Silicon has three isotopes. 92.23% is <sup>28<\/sup>Si and 4.67% is <sup>29<\/sup>Si. The remaining isotope has abundance:<\/p>\n            <p>100.00 \u2212 92.23 \u2212 4.67 = <strong>3.10%<\/strong><\/p>\n          <\/div>\n          <div class=\"ols-worked-step\">\n            <h3>Example: silicon mass<\/h3>\n            <p>If A<sub>r<\/sub> = 28.1 and the final isotope has mass X:<\/p>\n            <p>28.1 = [(28 \u00d7 92.23) + (29 \u00d7 4.67) + (X \u00d7 3.10)] \u00f7 100<\/p>\n          <\/div>\n          <div class=\"ols-worked-step\">\n            <h3>Rearranged result<\/h3>\n            <p>2810 = 2717.87 + 3.10X<\/p>\n            <p>92.13 = 3.10X<\/p>\n            <p>X = 29.7, so the isotope is treated as <strong><sup>30<\/sup>Si<\/strong>.<\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\"><p><strong>Exam focus:<\/strong> isotopic mass numbers are normally whole numbers, so a calculated value close to 30 represents silicon-30.<\/p><\/div>\n      <\/article>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">7<\/div><h2>Common Exam Points<\/h2><\/div>\n        <p>These points are useful for short calculation questions and explanations linked to mass spectra.<\/p>\n\n        <div class=\"ols-rule-list\">\n          <div class=\"ols-rule-item\"><h3>Use peak height as abundance<\/h3><p>In simple mass spectra, the peak height gives the relative abundance of that isotope.<\/p><\/div>\n          <div class=\"ols-rule-item\"><h3>Check the total abundance<\/h3><p>If the data are percentages, divide by 100. If they are relative abundances, divide by their total.<\/p><\/div>\n          <div class=\"ols-rule-item\"><h3>Use m\/z carefully<\/h3><p>If the charge is 1+, the m\/z value is usually treated as the relative isotopic mass. If the charge is not 1+, the mass-to-charge ratio must be considered directly.<\/p><\/div>\n          <div class=\"ols-rule-item\"><h3>Round only at the end<\/h3><p>Keep extra figures during the calculation, then round to the number of decimal places requested in the question.<\/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 the calculation method before moving on to exam-style questions.<\/p>\n\n        <div class=\"ols-h5p-grid\">\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-242\" class=\"h5p-iframe\" data-content-id=\"242\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"RAMCalculations.1 Drag: Relative Atomic Mass Key Concepts\"><\/iframe><\/div><\/div>\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-243\" class=\"h5p-iframe\" data-content-id=\"243\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"RAMCalculations.2 MCQ: RAM from Isotopic Abundance\"><\/iframe><\/div><\/div>\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-244\" class=\"h5p-iframe\" data-content-id=\"244\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"RAMCalculations.3 MCQ: RAM from a Chlorine Mass Spectrum\"><\/iframe><\/div><\/div>\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-245\" class=\"h5p-iframe\" data-content-id=\"245\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"RAMCalculations.4 MCQ: Missing Isotope Data\"><\/iframe><\/div><\/div>\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-338\" class=\"h5p-iframe\" data-content-id=\"338\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Relative Atomic Masses: Isotopic Abundance Dialog Cards\"><\/iframe><\/div><\/div>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-quicksnap-card\">\n        <h2>QuickSnap Summary<\/h2>\n        <p>A<sub>r<\/sub> is a weighted mean, so both isotopic mass and abundance matter.<\/p>\n\n        <div class=\"ols-snap-list\">\n          <div class=\"ols-snap-item\"><div class=\"ols-snap-number\">1<\/div><p>Multiply each isotope mass by its abundance.<\/p><\/div>\n          <div class=\"ols-snap-item\"><div class=\"ols-snap-number\">2<\/div><p>Add all of the mass \u00d7 abundance values.<\/p><\/div>\n          <div class=\"ols-snap-item\"><div class=\"ols-snap-number\">3<\/div><p>Divide by the total abundance. For percentages, this is normally 100.<\/p><\/div>\n          <div class=\"ols-snap-item\"><div class=\"ols-snap-number\">4<\/div><p>For a mass spectrum, use the m\/z values as isotope masses when the ions are 1+ and use peak heights as relative abundances.<\/p><\/div>\n        <\/div>\n      <\/section>\n\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            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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 1 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-the-periodic-table-topic-1\/\">\n                  View Course\n                <\/a>\n      \n              <\/div>\n      \n              <h2>\n                Master Atomic Structure and The Periodic Table for Edexcel 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 1 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      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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-the-periodic-table-topic-1\/\">\n              View Atomic Structure &#038; The Periodic Table Topic 1 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*{\n  box-sizing:border-box;\n}\n\n:root{\n  --ols-video-screen-w:1180;\n  --ols-video-screen-h:664;\n  --ols-video-screen-scale:1;\n\n  --ols-mcq-screen-w:1360;\n  --ols-mcq-screen-h:1130;\n  --ols-mcq-screen-scale:1;\n\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\/* ============================================================\n   GLOBAL SCENE SYSTEM\n============================================================ *\/\n\n.ols-combined-stage{\n  position:relative;\n  width:100vw;\n  height:100vh;\n  overflow:hidden;\n\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\n  width:100vw;\n  height:100vh;\n\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\n  width:5px;\n  height:0.85em;\n\n  background:#1C244B;\n\n  margin-left:8px;\n\n  transform:translateY(8px);\n\n  animation:olsBlink 0.8s infinite;\n}\n\n.cursor{\n  display:inline-block;\n\n  width:3px;\n  height:28px;\n\n  background:#1c244b;\n\n  margin-left:3px;\n\n  transform:translateY(5px);\n\n  animation:olsBlink 0.8s infinite;\n}\n\n@keyframes olsBlink{\n  0%,45%{\n    opacity:1;\n  }\n  46%,100%{\n    opacity:0;\n  }\n}\n\n.ols-combined-stage.ols-animation-paused *,\n.ols-combined-stage.ols-animation-paused *::before,\n.ols-combined-stage.ols-animation-paused *::after{\n  animation-play-state:paused !important;\n}\n\n\/* ============================================================\n   1. VIRTUAL LESSON PROMO\n============================================================ *\/\n\n.ols-video-stage{\n  width:100vw;\n  height:100vh;\n\n  display:flex;\n  justify-content:center;\n  align-items:center;\n\n  padding:0;\n  overflow:hidden;\n\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  position:absolute;\n  inset:0;\n  z-index:20;\n\n  display:flex;\n  justify-content:center;\n  align-items:center;\n\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  opacity:1;\n  visibility:visible;\n  pointer-events:none;\n}\n\n.ols-video-title-screen.hide{\n  animation:olsVideoTitleFadeOut 0.85s ease forwards;\n}\n\n@keyframes olsVideoTitleFadeOut{\n  to{\n    opacity:0;\n    visibility:hidden;\n  }\n}\n\n.ols-video-title-wrap{\n  max-width:1250px;\n  padding:0 34px;\n  text-align:center;\n}\n\n.ols-video-title{\n  margin:0;\n\n  font-family:Poppins,Arial,sans-serif;\n\n  font-size:clamp(52px,8vw,124px);\n  font-weight:600;\n  line-height:1.08;\n\n  color:#1C244B;\n\n  text-shadow:-9px 0 9px rgba(28,36,75,0.16);\n\n  letter-spacing:-0.045em;\n}\n\n#videoTitleText{\n  white-space:pre-wrap;\n}\n\n.ols-video-scene{\n  width:100%;\n  height:100%;\n\n  display:flex;\n  justify-content:center;\n  align-items:center;\n\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{\n  to{\n    opacity:1;\n  }\n}\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\n  transform:scale(var(--ols-video-screen-scale));\n  transform-origin:center center;\n\n  display:flex;\n  justify-content:center;\n  align-items:center;\n}\n\n.ols-video-card{\n  width:1180px;\n  height:664px;\n\n  border-radius:28px;\n  overflow:hidden;\n\n  background:#1C244B;\n\n  box-shadow:\n    0 28px 80px rgba(28,36,75,0.28);\n\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\n  aspect-ratio:16 \/ 9;\n  object-fit:cover;\n\n  border:0;\n}\n\n\/* ============================================================\n   2. MULTIPLE CHOICE FEEDBACK\n============================================================ *\/\n\n.ols-mcq-stage{\n  width:100vw;\n  height:100vh;\n\n  display:flex;\n  justify-content:center;\n  align-items:center;\n\n  padding:0;\n  overflow:hidden;\n\n  background:\n    radial-gradient(circle at top left,rgba(70,127,247,0.16),transparent 34%),\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\n}\n\n.ols-mcq-intro-screen{\n  position:absolute;\n  inset:0;\n  z-index:50;\n\n  display:flex;\n  justify-content:center;\n  align-items:center;\n\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  opacity:1;\n  visibility:visible;\n  pointer-events:none;\n}\n\n.ols-mcq-intro-screen.hide{\n  animation:olsMcqIntroFadeOut 0.85s ease forwards;\n}\n\n@keyframes olsMcqIntroFadeOut{\n  to{\n    opacity:0;\n    visibility:hidden;\n  }\n}\n\n.ols-mcq-intro-title-wrap{\n  max-width:1250px;\n  padding:0 34px;\n  text-align:center;\n}\n\n.ols-mcq-intro-title{\n  margin:0;\n\n  font-family:Poppins,Arial,sans-serif;\n\n  font-size:clamp(52px,8vw,124px);\n  font-weight:600;\n  line-height:1.08;\n\n  color:#1C244B;\n\n  text-shadow:-9px 0 9px rgba(28,36,75,0.16);\n\n  letter-spacing:-0.045em;\n}\n\n#mcqIntroTitleText{\n  white-space:pre-wrap;\n}\n\n.ols-mcq-scale-wrap{\n  width:calc(var(--ols-mcq-screen-w) * 1px);\n  height:calc(var(--ols-mcq-screen-h) * 1px);\n\n  transform:scale(var(--ols-mcq-screen-scale));\n  transform-origin:center center;\n\n  display:flex;\n  justify-content:center;\n  align-items:flex-start;\n}\n\n.ols-mcq-screen{\n  width:1360px;\n  height:1130px;\n\n  border-radius:22px;\n  overflow:hidden;\n\n  background:#eaf0ff;\n\n  box-shadow:\n    0 26px 70px rgba(28,36,75,0.22);\n\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{\n    opacity:0;\n    transform:translateY(24px) scale(0.96);\n  }\n  to{\n    opacity:1;\n    transform:translateY(0) scale(1);\n  }\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-ionic-table{\n  border-collapse:collapse;\n  width:500px;\n  margin-bottom:8px;\n  font-size:21px;\n  color:#111827;\n}\n\n.mcq-ionic-table th,\n.mcq-ionic-table td{\n  border:1.5px solid #c9ced8;\n  padding:12px 18px;\n  text-align:center;\n}\n\n.mcq-ionic-table th{\n  background:#f2f2f2;\n  font-weight:700;\n}\n\n.mcq-ionic-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:\n    opacity 0.25s ease,\n    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-option-row.selected .mcq-radio{\n  border-color:#4b5563;\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%{\n    opacity:0.65;\n    transform:translate(-50%,-50%) scale(1);\n  }\n  100%{\n    opacity:0;\n    transform:translate(-50%,-50%) scale(2.5);\n  }\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:\n    opacity 0.35s ease,\n    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\n  display:inline-flex;\n  justify-content:center;\n  align-items:center;\n\n  font-size:18px;\n  font-weight:700;\n\n  margin-right:12px;\n\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%{\n    opacity:1;\n    transform:scale(1.18);\n  }\n  100%{\n    opacity:1;\n    transform:scale(1);\n  }\n}\n\n.mcq-specific-feedback-text{\n  display:inline-block;\n\n  background:#fff4b8;\n  color:#111827;\n\n  padding:8px 16px;\n\n  font-size:22px;\n  line-height:1.35;\n\n  min-width:850px;\n  min-height:44px;\n}\n\n.mcq-submit-button{\n  position:absolute;\n  right:34px;\n  bottom:30px;\n\n  border:0;\n  border-radius:999px;\n\n  background:#1C244B;\n  color:#ffffff;\n\n  padding:14px 28px;\n\n  font-size:18px;\n  font-weight:600;\n\n  box-shadow:\n    0 14px 32px rgba(28,36,75,0.25);\n\n  cursor:default;\n\n  transform:translateY(0) scale(1);\n\n  transition:\n    transform 0.2s ease,\n    box-shadow 0.2s ease,\n    background 0.2s ease;\n}\n\n.mcq-submit-button.clicked{\n  transform:translateY(2px) scale(0.97);\n  background:#26315f;\n  box-shadow:\n    0 7px 18px rgba(28,36,75,0.22);\n}\n\n.mcq-general-feedback{\n  height:520px;\n\n  background:#fff3c9;\n  color:#8a6a00;\n\n  padding:26px 30px 28px;\n\n  font-size:23px;\n  line-height:1.34;\n\n  opacity:0;\n  transform:translateY(20px);\n\n  transition:\n    opacity 0.7s ease,\n    transform 0.7s ease;\n\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{\n  background:#111827;\n}\n\n.mcq-general-cursor{\n  background:#8a6a00;\n}\n\n\/* ============================================================\n   3. SHORT ANSWER FEEDBACK\n============================================================ *\/\n\n.ols-saq-stage{\n  width:100vw;\n  height:100vh;\n\n  display:flex;\n  justify-content:center;\n  align-items:center;\n\n  padding:0;\n  overflow:hidden;\n\n  background:\n    radial-gradient(circle at top left,rgba(70,127,247,0.16),transparent 34%),\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\n}\n\n.ols-saq-intro{\n  position:absolute;\n  inset:0;\n  z-index:50;\n\n  display:flex;\n  justify-content:center;\n  align-items:center;\n\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  opacity:1;\n  visibility:visible;\n  pointer-events:none;\n}\n\n.ols-saq-intro.hide{\n  animation:olsSaqIntroFadeOut 0.85s ease forwards;\n}\n\n@keyframes olsSaqIntroFadeOut{\n  to{\n    opacity:0;\n    visibility:hidden;\n  }\n}\n\n.ols-saq-intro-title-wrap{\n  max-width:1250px;\n  padding:0 34px;\n  text-align:center;\n}\n\n.ols-saq-intro-title{\n  margin:0;\n\n  font-family:Poppins,Arial,sans-serif;\n\n  font-size:clamp(52px,8vw,124px);\n  font-weight:600;\n  line-height:1.08;\n\n  color:#1C244B;\n\n  text-shadow:-9px 0 9px rgba(28,36,75,0.16);\n\n  letter-spacing:-0.045em;\n}\n\n#saqIntroTitleText{\n  white-space:pre-wrap;\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\n  transform:scale(var(--ols-saq-screen-scale));\n  transform-origin:center center;\n\n  display:flex;\n  justify-content:center;\n  align-items:flex-start;\n}\n\n.ols-saq-screen{\n  width:1360px;\n  height:965px;\n\n  border-radius:22px;\n  overflow:hidden;\n\n  background:#eaf0ff;\n\n  box-shadow:\n    0 26px 70px rgba(28,36,75,0.22);\n\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{\n    opacity:0;\n    transform:translateY(24px) scale(0.96);\n  }\n  to{\n    opacity:1;\n    transform:translateY(0) scale(1);\n  }\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\n  background:#f3f4f6;\n\n  border:2px solid #cfd6e3;\n  border-radius:8px;\n\n  padding:23px 26px;\n\n  font-size:24px;\n  line-height:1.55;\n\n  color:#4b5563;\n\n  position:relative;\n  overflow:hidden;\n}\n\n.saq-teacher-feedback{\n  height:630px;\n\n  background:#dff3e6;\n  color:#075f3b;\n\n  padding:28px 40px 30px;\n\n  font-size:23px;\n  line-height:1.47;\n\n  opacity:0;\n  transform:translateY(20px);\n\n  transition:\n    opacity 0.7s ease,\n    transform 0.7s ease;\n\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\/* ============================================================\n   SMALL WINDOW PROTECTION\n============================================================ *\/\n\n@media(max-width:900px){\n\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}\n<\/style>\n<\/head>\n\n<body>\n\n<div class=\"ols-combined-stage\">\n\n  <!-- ========================================================\n       SCENE 1: VIRTUAL LESSON\n  ========================================================= -->\n\n  <section id=\"sceneVideo\" class=\"ols-scene active\">\n\n    <div class=\"ols-video-stage\">\n\n      <div id=\"videoTitleScreen\" class=\"ols-video-title-screen\">\n\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\n      <\/div>\n\n      <section id=\"videoScene\" class=\"ols-video-scene\">\n\n        <div class=\"ols-video-scale-wrap\">\n\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\n        <\/div>\n\n      <\/section>\n\n    <\/div>\n\n  <\/section>\n\n  <!-- ========================================================\n       SCENE 2: MULTIPLE CHOICE FEEDBACK\n  ========================================================= -->\n\n  <section id=\"sceneMcq\" class=\"ols-scene\">\n\n    <div class=\"ols-mcq-stage\">\n\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\n        <main id=\"mcqScreen\" class=\"ols-mcq-screen\">\n\n          <section class=\"mcq-question-area\">\n\n            <p class=\"mcq-question-lead\">Some ionic radii are shown.<\/p>\n\n            <table class=\"mcq-ionic-table\">\n              <thead>\n                <tr>\n                  <th>Ion<\/th>\n                  <th>Ionic radius \/ nm<\/th>\n                <\/tr>\n              <\/thead>\n\n              <tbody>\n                <tr>\n                  <td>Na<sup>+<\/sup><\/td>\n                  <td>0.102<\/td>\n                <\/tr>\n\n                <tr>\n                  <td>K<sup>+<\/sup><\/td>\n                  <td>0.138<\/td>\n                <\/tr>\n\n                <tr>\n                  <td>F<sup>\u2212<\/sup><\/td>\n                  <td>0.133<\/td>\n                <\/tr>\n\n                <tr>\n                  <td>Cl<sup>\u2212<\/sup><\/td>\n                  <td>0.180<\/td>\n                <\/tr>\n              <\/tbody>\n            <\/table>\n\n            <p class=\"mcq-question-main\">Which compound has the strongest ionic bonding?<\/p>\n\n            <div class=\"mcq-options-wrap\">\n\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\">sodium chloride<\/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\">\n                <span class=\"mcq-radio\"><\/span>\n                <span class=\"mcq-radio-ripple\"><\/span>\n                <span class=\"mcq-option-label\">potassium chloride<\/span>\n              <\/div>\n\n              <div class=\"mcq-option-row\">\n                <span class=\"mcq-radio\"><\/span>\n                <span class=\"mcq-radio-ripple\"><\/span>\n                <span class=\"mcq-option-label\">sodium fluoride<\/span>\n              <\/div>\n\n              <div class=\"mcq-option-row\">\n                <span class=\"mcq-radio\"><\/span>\n                <span class=\"mcq-radio-ripple\"><\/span>\n                <span class=\"mcq-option-label\">potassium fluoride<\/span>\n              <\/div>\n\n            <\/div>\n\n            <button id=\"mcqSubmitButton\" class=\"mcq-submit-button\">Submit answer<\/button>\n\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\n        <\/main>\n\n      <\/div>\n\n    <\/div>\n\n  <\/section>\n\n  <!-- ========================================================\n       SCENE 3: SHORT ANSWER FEEDBACK\n  ========================================================= -->\n\n  <section id=\"sceneSaq\" class=\"ols-scene\">\n\n    <div class=\"ols-saq-stage\">\n\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 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Additionally, Mg\u00b2\u207a ions have a higher charge density than Na\u207a ions, further strengthening the metallic bonding.\\n\\n\" +\n\"Next time, include:\\n\" +\n\"\u2022 Ion charge: magnesium forms Mg\u00b2\u207a, sodium forms Na\u207a \u2713\\n\" +\n\"\u2022 Delocalised electrons: magnesium provides more electrons to the sea \u2713\\n\" +\n\"\u2022 Charge density: smaller, more highly charged ions create stronger attraction \u2713\\n\\n\" +\n\"You were close. 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abundances?<\/h3><p>Multiply each isotopic mass by its percentage abundance, add the results, then divide by 100.<\/p><\/div>\n          <div class=\"ols-faq-item\"><h3>How do you calculate A<sub>r<\/sub> from mass spectrum peaks?<\/h3><p>Use the m\/z values as isotope masses for 1+ ions, use the peak heights as relative abundances, then divide by the sum of the peak heights.<\/p><\/div>\n          <div class=\"ols-faq-item\"><h3>Why is chlorine&#8217;s A<sub>r<\/sub> about 35.5?<\/h3><p>Chlorine-35 is more abundant than chlorine-37, so the weighted mean lies closer to 35 than to 37.<\/p><\/div>\n          <div class=\"ols-faq-item\"><h3>What is the most common RAM calculation mistake?<\/h3><p>The most common mistake is dividing by 100 when the abundances are relative peak heights that do not total 100.<\/p><\/div>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-related-card\">\n        <h2>Related Topics<\/h2>\n        <p>Continue with the linked Topic 1 revision pages to connect RAM calculations with mass spectra, isotopes and ionisation energy.<\/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\/topic-1-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\/topic-1-atomic-structure-and-the-periodic-table\/mass-spectrometry\/predicting-diatomic-mass-spectra\/\">Predicting Diatomic Mass Spectra<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-atomic-structure-and-the-periodic-table\/atomic-structure\/\">Atomic Structure<\/a>\n        <\/div>\n      <\/section>\n    <!-- OLS Author Copyright Footprint \/ Attribution Card 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It may not be copied, reproduced, redistributed or adapted without written permission.<\/p>\n      <\/section>\n\n      <div class=\"ols-image-lightbox\" id=\"olsImageLightboxRamCalc9ch0\" aria-hidden=\"true\" role=\"dialog\" aria-modal=\"true\" aria-label=\"Expanded revision image\">\n        <div class=\"ols-image-lightbox-inner\">\n          <button class=\"ols-image-lightbox-close\" type=\"button\" aria-label=\"Close enlarged image\">\u00d7<\/button>\n          <img decoding=\"async\" class=\"ols-image-lightbox-img\" src=\"\" alt=\"\">\n        <\/div>\n      <\/div>\n\n      <script>\n        (function(){\n          var page = document.querySelector(\".ols-ram-calculations-9ch0-page\");\n          if (!page) return;\n          var lightbox = page.querySelector(\"#olsImageLightboxRamCalc9ch0\");\n          if (!lightbox) return;\n          var lightboxImage = lightbox.querySelector(\".ols-image-lightbox-img\");\n          var closeButton = 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