{"id":4516,"date":"2026-05-28T06:03:51","date_gmt":"2026-05-28T05:03:51","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-atomic-structure-and-the-periodic-table\/ionisation-energy\/"},"modified":"2026-06-02T09:20:19","modified_gmt":"2026-06-02T08:20:19","slug":"ionisation-energy","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-atomic-structure-and-the-periodic-table\/ionisation-energy\/","title":{"rendered":"Ionisation Energy"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-ionisation-energy-9ch0-landing-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-revision-layout {\n      display: grid;\n      grid-template-columns: 310px minmax(0, 1fr);\n      gap: 34px;\n      max-width: 1450px;\n      margin: 0 auto;\n      padding: 24px 20px 60px;\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: 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   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\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-related-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-related-card h2 { margin-bottom: 14px; }\n\n    .ols-note-card p,\n    .ols-note-card li,\n    .ols-related-card p,\n    .ols-attribution-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-related-card strong,\n    .ols-attribution-card strong {\n      font-weight: 700;\n      color: var(--navy);\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-ie-grid {\n      display: grid;\n      grid-template-columns: repeat(2, minmax(0, 1fr));\n      gap: 18px;\n      margin-top: 26px;\n    }\n\n    .ols-ie-card {\n      position: relative;\n      display: grid;\n      grid-template-rows: auto 1fr auto;\n      min-height: 285px;\n      padding: 24px;\n      border-radius: 24px;\n      border: 1px solid rgba(28, 36, 75, 0.13);\n      background:\n        radial-gradient(circle at top right, rgba(37, 99, 235, 0.13), transparent 34%),\n        linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n      color: var(--navy);\n      text-decoration: none;\n      overflow: hidden;\n      box-shadow: var(--inner-shadow);\n      transition: transform 0.24s ease, box-shadow 0.24s ease, border-color 0.24s ease, background 0.24s ease;\n    }\n\n    .ols-ie-card:hover {\n      transform: translateY(-6px);\n      border-color: rgba(37, 99, 235, 0.28);\n      box-shadow: 0 24px 52px rgba(28, 36, 75, 0.15);\n      color: var(--navy);\n    }\n\n    .ols-ie-card::before {\n      content: \"\";\n      position: absolute;\n      top: -60px;\n      right: -60px;\n      width: 145px;\n      height: 145px;\n      border-radius: 50%;\n      background: rgba(37, 99, 235, 0.08);\n      transition: transform 0.28s ease, background 0.28s ease;\n    }\n\n    .ols-ie-card:hover::before {\n      transform: scale(1.22);\n      background: rgba(37, 99, 235, 0.13);\n    }\n\n    .ols-ie-visual {\n      position: relative;\n      z-index: 1;\n      min-height: 94px;\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      margin-bottom: 18px;\n    }\n\n    .ols-ie-icon {\n      position: relative;\n      width: 142px;\n      height: 94px;\n    }\n\n    .ols-ie-line,\n    .ols-ie-axis,\n    .ols-ie-curve,\n    .ols-ie-peak,\n    .ols-ie-orbit,\n    .ols-ie-nucleus,\n    .ols-ie-electron,\n    .ols-ie-arrow,\n    .ols-ie-label-mini,\n    .ols-ie-bar,\n    .ols-ie-point {\n      position: absolute;\n      display: block;\n    }\n\n    .ols-ie-nucleus {\n      left: 55px;\n      top: 36px;\n      width: 26px;\n      height: 26px;\n      border-radius: 50%;\n      background: var(--navy);\n      box-shadow: 0 8px 18px rgba(28, 36, 75, 0.22);\n    }\n\n    .ols-ie-nucleus::after {\n      content: \"+\";\n      position: absolute;\n      inset: 0;\n      display: grid;\n      place-items: center;\n      color: #ffffff;\n      font-size: 18px;\n      font-weight: 800;\n    }\n\n    .ols-ie-orbit {\n      left: 28px;\n      top: 18px;\n      width: 82px;\n      height: 58px;\n      border: 3px solid rgba(37, 99, 235, 0.20);\n      border-radius: 50%;\n      transform: rotate(-16deg);\n    }\n\n    .ols-ie-electron {\n      width: 17px;\n      height: 17px;\n      border-radius: 50%;\n      background: var(--blue);\n      box-shadow: 0 6px 14px rgba(37, 99, 235, 0.24);\n    }\n\n    .ols-ie-electron::after {\n      content: \"\u2212\";\n      position: absolute;\n      inset: 0;\n      display: grid;\n      place-items: center;\n      color: #ffffff;\n      font-size: 14px;\n      font-weight: 800;\n    }\n\n    .ols-ie-intro .ols-ie-electron.e1 { left: 93px; top: 21px; }\n    .ols-ie-intro .ols-ie-electron.e2 { left: 107px; top: 44px; transform: scale(0.8); opacity: 0.86; }\n    .ols-ie-intro .ols-ie-arrow { left: 111px; top: 28px; width: 30px; height: 3px; border-radius: 999px; background: rgba(201, 151, 58, 0.86); transform: rotate(-18deg); }\n    .ols-ie-intro .ols-ie-arrow::after { content: \"\"; position: absolute; right: -1px; top: 50%; transform: translateY(-50%); border-left: 10px solid rgba(201,151,58,0.86); border-top: 6px solid transparent; border-bottom: 6px solid transparent; }\n\n    .ols-ie-successive .ols-ie-axis.x,\n    .ols-ie-period .ols-ie-axis.x,\n    .ols-ie-group .ols-ie-axis.x { left: 13px; right: 10px; bottom: 20px; height: 3px; background: rgba(28,36,75,0.32); border-radius: 999px; }\n\n    .ols-ie-successive .ols-ie-axis.y,\n    .ols-ie-period .ols-ie-axis.y,\n    .ols-ie-group .ols-ie-axis.y { left: 18px; top: 14px; bottom: 18px; width: 3px; background: rgba(28,36,75,0.32); border-radius: 999px; }\n\n    .ols-ie-successive .ols-ie-bar { bottom: 20px; width: 8px; border-radius: 999px 999px 0 0; background: var(--blue); }\n    .ols-ie-successive .ols-ie-bar.b1 { left: 40px; height: 21px; }\n    .ols-ie-successive .ols-ie-bar.b2 { left: 62px; height: 31px; background: var(--blue); }\n    .ols-ie-successive 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bottom: 31px; }\n    .ols-ie-period .ols-ie-point.p2 { left: 61px; bottom: 40px; }\n    .ols-ie-period .ols-ie-point.p3 { left: 88px; bottom: 49px; background: var(--navy); }\n    .ols-ie-period .ols-ie-point.p4 { left: 115px; bottom: 62px; background: var(--gold); }\n    .ols-ie-period .ols-ie-label-mini { right: 8px; top: 6px; color: var(--blue); font-size: 12px; font-weight: 800; }\n\n    .ols-ie-group .ols-ie-bar { bottom: 20px; width: 10px; border-radius: 999px 999px 0 0; background: var(--blue); }\n    .ols-ie-group .ols-ie-bar.b1 { left: 40px; height: 64px; background: var(--navy); }\n    .ols-ie-group .ols-ie-bar.b2 { left: 64px; height: 49px; background: var(--blue); }\n    .ols-ie-group .ols-ie-bar.b3 { left: 88px; height: 34px; background: var(--gold); }\n    .ols-ie-group .ols-ie-bar.b4 { left: 112px; height: 22px; background: #c81e1e; }\n    .ols-ie-group .ols-ie-arrow { left: 98px; top: 22px; width: 3px; height: 42px; border-radius: 999px; background: rgba(201, 151, 58, 0.86); }\n    .ols-ie-group .ols-ie-arrow::after { content: \"\"; position: absolute; left: 50%; bottom: -1px; transform: translateX(-50%); border-top: 10px solid rgba(201,151,58,0.86); border-left: 6px solid transparent; border-right: 6px solid transparent; }\n\n    .ols-ie-card h3 {\n      position: relative;\n      z-index: 1;\n      margin: 0 0 10px;\n      font-size: 23px;\n      line-height: 1.2;\n      font-weight: 800;\n      letter-spacing: -0.02em;\n      color: #111827;\n    }\n\n    .ols-ie-card p {\n      position: relative;\n      z-index: 1;\n      margin: 0;\n      font-size: 15px;\n      line-height: 1.6;\n      font-weight: 300;\n      color: var(--body-text);\n    }\n\n    .ols-ie-card,\n    .ols-ie-card *,\n    .ols-ie-card:hover,\n    .ols-ie-card:hover *,\n    .ols-related-item,\n    .ols-related-item *,\n    .ols-related-item:hover,\n    .ols-related-item:hover * {\n      text-decoration: none !important;\n    }\n\n    .ols-ie-meta {\n      position: relative;\n  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   .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 0%, #f8fbff 100%);\n    }\n\n    .ols-attribution-card p {\n      margin: 0;\n      font-size: 14px;\n      color: var(--grey-text);\n    }\n\n    @media (max-width: 1050px) {\n      .ols-revision-layout { grid-template-columns: 1fr; }\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-revision-layout { padding: 14px 12px 44px; }\n      .ols-title-card, .ols-note-card, .ols-related-card, .ols-attribution-card { padding: 24px 18px; border-radius: 22px; }\n      .ols-note-title { align-items: flex-start; }\n      .ols-ie-grid, .ols-related-grid { grid-template-columns: 1fr; }\n\n      .ols-author { align-items: flex-start; padding: 22px 18px; border-radius: 22px; }\n      .ols-author-avatar-img { width: 72px; height: 72px; }\n      .ols-author-title { font-size: 24px; }\n      .ols-author-description { font-size: 15px; }\n      .ols-ie-card { min-height: 255px; }\n    }\n\n    \/* =========================================================\n       SIMPLE COLOURFUL LANDING PAGE CARD VISUALS\n       Uses robust symbols rather than complex mini-diagrams.\n    ========================================================= *\/\n\n    .ols-ie-grid {\n      grid-template-columns: repeat(2, minmax(0, 1fr)) !important;\n      gap: 22px !important;\n    }\n\n    .ols-ie-card {\n      display: flex !important;\n      flex-direction: column !important;\n      padding: 0 !important;\n      min-height: 0 !important;\n      border-radius: 24px !important;\n      overflow: hidden !important;\n      background: #ffffff !important;\n      box-shadow: 0 14px 34px rgba(28, 36, 75, 0.10) !important;\n      transition:\n        transform 0.28s cubic-bezier(0.34, 1.56, 0.64, 1),\n        box-shadow 0.28s ease,\n        border-color 0.28s ease !important;\n    }\n\n    .ols-ie-card:hover {\n      transform: translateY(-10px) scale(1.02) !important;\n      box-shadow: 0 28px 56px rgba(28, 36, 75, 0.16) !important;\n      border-color: rgba(37, 99, 235, 0.35) !important;\n    }\n\n    .ols-ie-card::before {\n      display: none !important;\n    }\n\n    .ols-ie-card-img-wrap {\n      position: relative;\n      width: 100%;\n      aspect-ratio: 4 \/ 3;\n      overflow: hidden;\n      background: var(--soft-blue);\n    }\n\n    .ols-ie-card-img-wrap::after {\n      content: \"\";\n      position: absolute;\n      inset: 0;\n      background: linear-gradient(180deg, transparent 40%, rgba(28, 36, 75, 0.22) 100%);\n      opacity: 0;\n      transition: opacity 0.28s ease;\n      z-index: 1;\n    }\n\n    .ols-ie-card:hover .ols-ie-card-img-wrap::after {\n      opacity: 1;\n    }\n\n    .ols-ie-card-num {\n      position: absolute;\n      top: 14px;\n      left: 14px;\n      width: 34px;\n      height: 34px;\n      border-radius: 50%;\n      background: var(--navy);\n      color: #ffffff;\n      font-size: 13px;\n      font-weight: 800;\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      z-index: 4;\n      box-shadow: 0 6px 16px rgba(28, 36, 75, 0.30);\n    }\n\n    .ols-ie-card-status {\n      position: absolute;\n      top: 14px;\n      right: 14px;\n      padding: 5px 11px;\n      border-radius: 999px;\n      background: #eaf3de;\n      color: #3B6D11;\n      font-size: 10px;\n      font-weight: 800;\n      letter-spacing: 0.01em;\n      z-index: 4;\n      box-shadow: 0 6px 16px rgba(28, 36, 75, 0.12);\n    }\n\n    .ols-ie-card-body {\n      padding: 20px 20px 24px;\n      flex: 1;\n      display: flex;\n      flex-direction: column;\n      gap: 8px;\n      background: #ffffff;\n    }\n\n    .ols-ie-card-body h3 {\n      margin: 0 !important;\n      font-size: 18px 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     width: min(88%, 280px);\n        min-height: 140px;\n      }\n    }\n\n\n  <\/style>\n\n  <div class=\"ols-revision-layout\">\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', 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<header class=\"ols-title-card\">\n        <h1>Ionisation Energy<\/h1>\n        <p class=\"ols-page-intro\">Use this landing page to move quickly between the key ionisation energy revision pages for Topic 1. Each card links to a focused page covering first ionisation energy, successive ionisation energy, periodic trends and group trends.<\/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          <img decoding=\"async\" class=\"ols-author-avatar-img\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\" alt=\"Dr. Mohammed Al-Fatah\">\n\n          <div class=\"ols-author-content\">\n            <h2 class=\"ols-author-title\">Written by:<br><span>Dr. Mohammed Al-Fatah<\/span><\/h2>\n            <p class=\"ols-author-description\">Chemistry specialist revision notes for A Level Chemistry.<\/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\"><\/path>\n              <\/svg>\n              View LinkedIn Profile\n            <\/a>\n          <\/div>\n        <\/div>\n      <\/header>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">1<\/div>\n          <h2>Choose an Ionisation Energy Page<\/h2>\n        <\/div>\n\n        <p>Ionisation energy measures the energy required to remove an electron from a gaseous atom or ion. These pages build from the definition of first ionisation energy through to successive ionisation energy patterns and the main periodic trends across a period and down a group.<\/p>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Key idea:<\/strong> Ionisation energy depends on nuclear charge, atomic radius, electron shielding and the subshell from which the electron is removed.<\/p>\n        <\/div>\n\n        <div class=\"ols-ie-grid\">\n          <a class=\"ols-ie-card ols-ie-card--available\" 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\/\">\n            <div class=\"ols-ie-card-img-wrap\">\n              <div class=\"ols-ie-visual ols-ie-visual--intro\">\n                <div class=\"ols-ie-visual-panel\">\n                  <div class=\"ols-ie-visual-kicker\">Electron removal<\/div>\n                  <div class=\"ols-ie-symbol\" aria-hidden=\"true\">M \u2192 M\u207a<\/div>\n                  <div class=\"ols-ie-visual-main\">First<br>Ionisation<\/div>\n                  <div class=\"ols-ie-visual-sub\">definition, state symbols and attraction<\/div>\n                <\/div>\n              <\/div>\n              <div class=\"ols-ie-card-num\">1<\/div>\n              <span class=\"ols-ie-card-status\">Available<\/span>\n            <\/div>\n            <div class=\"ols-ie-card-body\">\n              <h3>Introduction to Ionisation Energy<\/h3>\n              <p>Revise the definition of first ionisation energy, state symbols and the factors that affect electron removal.<\/p>\n              <span class=\"ols-ie-meta\">Start revising<\/span>\n            <\/div>\n          <\/a>\n\n          <a class=\"ols-ie-card ols-ie-card--available\" 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\/\">\n            <div class=\"ols-ie-card-img-wrap\">\n              <div class=\"ols-ie-visual ols-ie-visual--successive\">\n                <div class=\"ols-ie-visual-panel\">\n                  <div class=\"ols-ie-visual-kicker\">Energy jumps<\/div>\n                  <div class=\"ols-ie-symbol small\" aria-hidden=\"true\">IE\u2081 &lt; IE\u2082 &lt; IE\u2083<\/div>\n                  <div class=\"ols-ie-visual-main\">Successive<br>Values<\/div>\n                  <div class=\"ols-ie-visual-sub\">large jumps reveal electron shells<\/div>\n                <\/div>\n              <\/div>\n              <div class=\"ols-ie-card-num\">2<\/div>\n              <span class=\"ols-ie-card-status\">Available<\/span>\n            <\/div>\n            <div class=\"ols-ie-card-body\">\n              <h3>Successive Ionisation Energies<\/h3>\n              <p>Use successive ionisation energy data to identify electron shells, group number and large jumps between energy levels.<\/p>\n              <span class=\"ols-ie-meta\">Start revising<\/span>\n            <\/div>\n          <\/a>\n\n          <a class=\"ols-ie-card ols-ie-card--available\" 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\/\">\n            <div class=\"ols-ie-card-img-wrap\">\n              <div class=\"ols-ie-visual ols-ie-visual--period\">\n                <div class=\"ols-ie-visual-panel\">\n                  <div class=\"ols-ie-visual-kicker\">Across a period<\/div>\n                  <div class=\"ols-ie-symbol\" aria-hidden=\"true\">IE \u2191<\/div>\n                  <div class=\"ols-ie-visual-main\">Period<br>Trends<\/div>\n                  <div class=\"ols-ie-visual-sub\">nuclear charge, radius and subshells<\/div>\n                <\/div>\n              <\/div>\n              <div class=\"ols-ie-card-num\">3<\/div>\n              <span class=\"ols-ie-card-status\">Available<\/span>\n            <\/div>\n            <div class=\"ols-ie-card-body\">\n              <h3>Trends in a Period<\/h3>\n              <p>Explain why first ionisation energy generally increases across a period, including the small drops at key points.<\/p>\n              <span class=\"ols-ie-meta\">Start revising<\/span>\n            <\/div>\n          <\/a>\n\n          <a class=\"ols-ie-card ols-ie-card--available\" 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\/\">\n            <div class=\"ols-ie-card-img-wrap\">\n              <div class=\"ols-ie-visual ols-ie-visual--group\">\n                <div class=\"ols-ie-visual-panel\">\n                  <div class=\"ols-ie-visual-kicker\">Down a group<\/div>\n                  <div class=\"ols-ie-symbol\" aria-hidden=\"true\">IE \u2193<\/div>\n                  <div class=\"ols-ie-visual-main\">Group<br>Trends<\/div>\n                  <div class=\"ols-ie-visual-sub\">shielding and atomic radius increase<\/div>\n                <\/div>\n              <\/div>\n              <div class=\"ols-ie-card-num\">4<\/div>\n              <span class=\"ols-ie-card-status\">Available<\/span>\n            <\/div>\n            <div class=\"ols-ie-card-body\">\n              <h3>Trends in a Group<\/h3>\n              <p>Explain why first ionisation energy decreases down a group as shielding and atomic radius increase.<\/p>\n              <span class=\"ols-ie-meta\">Start revising<\/span>\n            <\/div>\n          <\/a>\n        <\/div>\n\n      <\/article>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">\u2713<\/div>\n          <h2>How to Use These Pages<\/h2>\n        <\/div>\n\n        <p>Start with the definition of first ionisation energy so that your equations, state symbols and explanations are accurate. Then move to successive ionisation energy, because the large jumps help reveal electronic structure. Finally, use the period and group trend pages to practise explaining patterns using nuclear charge, shielding, atomic radius and subshell energy.<\/p>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Exam focus:<\/strong> When explaining ionisation energy, always connect the trend to attraction between the nucleus and the outer electron. Use precise factors rather than vague statements about atoms being bigger or smaller.<\/p>\n        <\/div>\n      <\/article>\n\n      <section class=\"ols-related-card\">\n        <h2>Related Topic 1 Pages<\/h2>\n        <p>Use these pages to connect ionisation energy with atomic structure, electron configuration and mass spectrometry.<\/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\/atomic-structure\/\">Atomic Structure<\/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\/\">Mass Spectrometry<\/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\/electron-configuration\/\">Electron Configuration<\/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\/ionisation-energy\/introduction-to-ionisation-energy\/\">Introduction to Ionisation Energy<\/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\/ionisation-energy\/successive-ionisation-energies\/\">Successive Ionisation Energy<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/\">Next Topic: Bonding &amp; Structure<\/a>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-attribution-card\">\n        <p><strong>Copyright notice:<\/strong> This revision page, including its written explanations, layout and teaching sequence, is produced for Online Learning System by Dr. Mohammed Al-Fatah. It is intended for student revision and may not be copied, redistributed or republished without permission.<\/p>\n      <\/section>\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\/topic-1-atomic-structure-and-the-periodic-table\/ionisation-energy\/#webpage\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-atomic-structure-and-the-periodic-table\/ionisation-energy\/\",\n            \"name\": \"Ionisation Energy - Edexcel A Level Chemistry Revision Notes\",\n            \"description\": \"Edexcel A Level Chemistry landing page for ionisation energy, including first ionisation energy, successive ionisation energies, trends in a period and trends in a group.\",\n            \"inLanguage\": \"en-GB\",\n            \"isPartOf\": {\n              \"@type\": \"WebSite\",\n              \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/#website\",\n              \"name\": \"Online Learning System\",\n              \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/\"\n            },\n            \"about\": [\n              {\n                \"@type\": \"Thing\",\n                \"name\": \"Ionisation energy\"\n              },\n              {\n                \"@type\": \"Thing\",\n                \"name\": \"First ionisation energy\"\n              },\n              {\n                \"@type\": \"Thing\",\n                \"name\": \"Successive ionisation energy\"\n              },\n              {\n                \"@type\": \"Thing\",\n                \"name\": \"Periodic trends\"\n              }\n            ],\n            \"author\": {\n              \"@type\": \"Person\",\n              \"name\": \"Dr. Mohammed Al-Fatah\",\n              \"url\": \"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\"\n            },\n            \"publisher\": {\n              \"@type\": \"Organization\",\n              \"name\": \"Online Learning System\",\n              \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/\"\n            }\n          },\n          {\n            \"@type\": \"BreadcrumbList\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-atomic-structure-and-the-periodic-table\/ionisation-energy\/#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\",\n                \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/\"\n              },\n              {\n                \"@type\": \"ListItem\",\n                \"position\": 4,\n                \"name\": \"Topic 1 Atomic Structure and The Periodic Table\",\n                \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-atomic-structure-and-the-periodic-table\/\"\n              },\n              {\n                \"@type\": \"ListItem\",\n                \"position\": 5,\n                \"name\": \"Ionisation Energy\",\n                \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-1-atomic-structure-and-the-periodic-table\/ionisation-energy\/\"\n              }\n            ]\n          }\n        ]\n      }\n      <\/script>\n    <\/main>\n  <\/div>\n<\/section>\n","protected":false},"excerpt":{"rendered":"<p>Revision Notes \/ A Level Chemistry \/ Edexcel \/ Topic 1 Atomic Structure &amp; The Periodic Table \/ Ionisation Energy Ionisation Energy Use this landing page to move quickly between the key ionisation energy revision pages for Topic 1. 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