{"id":3997,"date":"2026-05-21T04:56:54","date_gmt":"2026-05-21T03:56:54","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/trends-in-a-group\/"},"modified":"2026-06-28T05:52:45","modified_gmt":"2026-06-28T04:52:45","slug":"trends-in-a-group","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/trends-in-a-group\/","title":{"rendered":"Trends in a Group"},"content":{"rendered":"\n<!--\n===============================================================================\nONLINE LEARNING SYSTEM COPYRIGHT NOTICE\n\u00a9 Online Learning System. 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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 {\n        font-size: 24px;\n      }\n\n      .ols-author-description {\n        font-size: 15px;\n      }\n\n      .ols-course-cta-atomic-structure .ols-course-cta-card {\n        padding: 20px;\n        border-radius: 24px;\n      }\n\n      .ols-course-cta-atomic-structure .ols-course-button,\n      .ols-course-cta-atomic-structure .ols-course-button-top {\n        width: 100%;\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 2 Atomic Structure and The Periodic Table<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/atomic-structure\/\">Atomic Structure<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/\">Mass Spectrometry<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/the-mass-spectrometer\/\">The Mass Spectrometer<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/ram-calculations\/\">RAM Calculations<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/predicting-diatomic-mass-spectra\/\">Predicting Diatomic Mass Spectra<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/identifying-compounds-from-mass-spectra\/\">Identifying Compounds from Mass Spectra<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/quantum-model\/\">Quantum Model<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/\">Ionisation Energy<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/introduction-to-ionisation-energy\/\">Introduction to Ionisation Energy<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/successive-ionisation-energy\/\">Successive Ionisation Energy<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/trends-in-a-period\/\">Trends in a Period<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/trends-in-a-group\/\">Trends in a Group<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Next Topics<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-3-bonding-structure\/\">Bonding &amp; Structure<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/\">Organic Chemistry &amp; Alkanes<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-5-alkenes\/\">Alkenes<\/a>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n<\/aside>\r\n\r\n<script>\r\n(function() {\r\n  function normalisePath(path) {\r\n    return String(path || '')\r\n      .split('?')[0]\r\n      .split('#')[0]\r\n      .replace(\/\\\/+$\/, '')\r\n      .toLowerCase();\r\n  }\r\n\r\n  function highlightActive() {\r\n    var sidebar = document.querySelector('.ols-sidebar');\r\n    if 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href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Edexcel International<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/\">Topic 2 Atomic Structure &amp; The Periodic Table<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/\">Ionisation Energy<\/a> \/\n        <span>Trends in a Group<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Trends in a Group<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to first ionisation energy trends down a group, including atomic radius, shielding, nuclear charge and why outer electrons become easier to remove.<\/p>\n\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Unit 1: Structure, Bonding and Introduction to Organic Chemistry<\/div>\n          <div class=\"ols-badge\">Topic 2: Atomic Structure &amp; The Periodic Table<\/div>\n          <div class=\"ols-badge\">WCH11\/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          <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            <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\"><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><\/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\"><div class=\"ols-note-icon\">1<\/div><h2>What Does Going Down a Group Mean?<\/h2><\/div>\n        <p>A <strong>group<\/strong> is a vertical column in the periodic table. Elements in the same group have the same number of outer-shell electrons, so they often show similar chemical behaviour.<\/p>\n        <p>When you go down a group, each element has one more occupied electron shell than the element above it. This increases the distance between the nucleus and the outer electron.<\/p>\n        <div class=\"ols-key-box\">\n          <p><strong>Core idea:<\/strong> down a group, the outer electron is further from the nucleus and is shielded by more inner electron shells.<\/p>\n        <\/div>\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Classification-of-elements-in-blocks.webp\" alt=\"Periodic table classification showing s, p, d and f blocks\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>Groups are vertical columns in the periodic table. The block also helps identify which subshell receives the outer electrons.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">2<\/div><h2>Atomic Radius Increases Down a Group<\/h2><\/div>\n        <p><strong>Atomic radius increases down a group<\/strong> because each element has an additional main electron shell.<\/p>\n        <p>The outer electron is further from the nucleus, so the attraction between the nucleus and the outer electron becomes weaker. This increased distance is one of the main reasons ionisation energy decreases down a group.<\/p>\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Atomic-radius-increase-in-Group-2.webp\" alt=\"Atomic radius increasing down Group 2\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>Each element lower in Group 2 has an extra occupied electron shell, so its outer electron is further from the nucleus.<\/p>\n          <\/div>\n        <\/div>\n        <div class=\"ols-key-box\">\n          <p><strong>Exam phrase:<\/strong> the outer electron is further from the nucleus because there are more occupied electron shells.<\/p>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">3<\/div><h2>Shielding Increases Down a Group<\/h2><\/div>\n        <p>As atoms get larger down a group, there are more inner shells between the nucleus and the outer electron. These inner shells <strong>shield<\/strong> the outer electron from the full attraction of the nucleus.<\/p>\n        <p>This means the outer electron experiences a lower effective nuclear attraction, even though the total number of protons in the nucleus has increased.<\/p>\n        <div class=\"ols-definition-box\">\n          <p><strong>Shielding:<\/strong> the reduction in attraction between the nucleus and an outer electron due to repulsion from inner-shell electrons.<\/p>\n        <\/div>\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Factor down a group<\/th>\n                <th>What happens?<\/th>\n                <th>Effect on the outer electron<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Factor down a group\">Number of shells<\/td>\n                <td data-label=\"What happens?\">Increases<\/td>\n                <td data-label=\"Effect on the outer electron\">Outer electron is further from the nucleus.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Factor down a group\">Shielding<\/td>\n                <td data-label=\"What happens?\">Increases<\/td>\n                <td data-label=\"Effect on the outer electron\">Inner shells reduce the attraction felt by the outer electron.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Factor down a group\">Nuclear charge<\/td>\n                <td data-label=\"What happens?\">Increases<\/td>\n                <td data-label=\"Effect on the outer electron\">More protons increase attraction, but this is outweighed by extra shells and shielding.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Factor down a group\">First ionisation energy<\/td>\n                <td data-label=\"What happens?\">Decreases<\/td>\n                <td data-label=\"Effect on the outer electron\">Less energy is needed to remove the outer electron.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card orange\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">4<\/div><h2>First Ionisation Energy Decreases Down a Group<\/h2><\/div>\n        <p>First ionisation energy generally <strong>decreases down a group<\/strong>. This means it becomes easier to remove the outer electron from atoms lower in the group.<\/p>\n        <p>The nuclear charge does increase because atoms lower in the group have more protons. However, the effect of the extra shells and increased shielding is greater. The outer electron is less strongly attracted to the nucleus, so less energy is needed to remove it.<\/p>\n        <div class=\"ols-key-box\">\n          <p><strong>Best exam answer:<\/strong> down a group, there are more occupied shells, the outer electron is further from the nucleus and shielding increases. These effects outweigh the increased nuclear charge.<\/p>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">5<\/div><h2>Group Trend Compared with Period Trend<\/h2><\/div>\n        <p>It is useful to separate <strong>down a group<\/strong> from <strong>across a period<\/strong>. Across a period, electrons are added to the same main shell, so shielding remains similar and atomic radius generally decreases.<\/p>\n        <p>Down a group, electrons are added to new shells. This gives a larger atomic radius and more shielding, so first ionisation energy decreases.<\/p>\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Atomic-radius-trend-across-Period-3.webp\" alt=\"Atomic radius trend across Period 3\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>Across a period, atomic radius decreases because nuclear charge increases while shielding remains similar.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">6<\/div><h2>Avoid Mixing Up Ionisation Energy with Melting Point<\/h2><\/div>\n        <p>Ionisation energy is about removing an electron from a gaseous atom. It is not the same as melting point or boiling point, which depend on bonding and structure.<\/p>\n        <p>Across Period 3, melting and boiling points do not follow the same pattern as ionisation energy because sodium, magnesium and aluminium are metallic, silicon is giant covalent, and phosphorus, sulfur, chlorine and argon are simple molecular or monatomic.<\/p>\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Melting-and-boiling-points-across-Period-3.webp\" alt=\"Melting and boiling points across Period 3\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>Physical property trends depend on bonding and structure, so they should not be explained using ionisation energy arguments alone.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">7<\/div><h2>Common Exam Points<\/h2><\/div>\n        <ul>\n          <li>First ionisation energy is the energy needed to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.<\/li>\n          <li>Down a group, the number of occupied electron shells increases.<\/li>\n          <li>The atomic radius increases because the outer electron is further from the nucleus.<\/li>\n          <li>Shielding increases because there are more inner shells between the nucleus and the outer electron.<\/li>\n          <li>Nuclear charge increases down the group, but this does not reverse the trend.<\/li>\n          <li>The effect of increased distance and shielding outweighs the increase in nuclear charge.<\/li>\n          <li>First ionisation energy decreases, so the outer electron is removed more easily.<\/li>\n        <\/ul>\n      <\/article>\n\n      <section class=\"ols-h5p-card\">\n        <h2>Check Your Understanding<\/h2>\n        <p>Use these short tasks to test the key reasons why first ionisation energy decreases down a group.<\/p>\n        <div class=\"ols-h5p-grid\">\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-275\" class=\"h5p-iframe\" data-content-id=\"275\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T2.4.13 Drag: Trends in a Group Key Concepts\"><\/iframe><\/div><\/div>\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-279\" class=\"h5p-iframe\" data-content-id=\"279\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T2.4.14 MCQ: First Ionisation Energy Down a Group\"><\/iframe><\/div><\/div>\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-280\" class=\"h5p-iframe\" data-content-id=\"280\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T2.4.15 MCQ: Shielding Down a Group\"><\/iframe><\/div><\/div>\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-281\" class=\"h5p-iframe\" data-content-id=\"281\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T2.4.16 MCQ: Nuclear Charge Down a Group\"><\/iframe><\/div><\/div>\n          <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-351\" class=\"h5p-iframe\" data-content-id=\"351\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Ionisation Energy: Trends in a Group Dialog Cards\"><\/iframe><\/div><\/div>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-quicksnap-card\">\n        <h2>QuickSnap<\/h2>\n        <p>This text summary condenses the page into the essential exam ideas.<\/p>\n        <ul class=\"ols-quicksnap-list\">\n          <li><strong>Down a group, atomic radius increases<\/strong> because each element has an additional occupied electron shell.<\/li>\n          <li><strong>The outer electron is further from the nucleus<\/strong>, so the attraction between the nucleus and the outer electron is weaker.<\/li>\n          <li><strong>Shielding increases<\/strong> because there are more inner shells between the nucleus and the outer electron.<\/li>\n          <li><strong>Nuclear charge increases<\/strong>, but the effect of extra shells and shielding outweighs this.<\/li>\n          <li><strong>First ionisation energy decreases<\/strong>, so less energy is needed to remove the outer electron.<\/li>\n          <li><strong>Best exam answers<\/strong> explicitly use distance from the nucleus, shielding, nuclear charge and attraction.<\/li>\n        <\/ul>\n      <\/section>\n\n      <section class=\"ols-course-cta-atomic-structure\" id=\"olsCourseCtaAtomicStructure002\">\n  <style>\n    .ols-course-cta-atomic-structure,\n    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Course\n          <\/div>\n\n          <a class=\"ols-course-button ols-course-button-top\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/atomic-structure-and-periodic-table-edexcel-t2\/\">\n            View Course\n          <\/a>\n\n        <\/div>\n\n        <h2>\n          Master Atomic Structure and The Periodic Table for Edexcel International A Level Chemistry\n        <\/h2>\n\n      <\/div>\n\n    <\/div>\n\n    <div class=\"ols-course-cta-intro-stats\">\n\n      <p class=\"ols-course-cta-intro\">\n        Continue from these free revision notes into the full Topic 2 Atomic Structure and The Periodic Table course, with guided video teaching, diagnostic MCQ practice, teacher-marked short-answer questions and a specification assignment with a personalised progress report.\n      <\/p>\n\n      <div class=\"ols-course-cta-stats\">\n\n        <div class=\"ols-course-stat\">\n          <span>Guided learning<\/span>\n          <strong>18 hours<\/strong>\n        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every answer choice.\n        <\/p>\n      <\/div>\n\n      <div class=\"ols-course-feature\">\n        <h3>Teacher-marked SAQs<\/h3>\n        <p>\n          Submit written exam responses and receive chemistry specialist feedback with improvement guidance.\n        <\/p>\n      <\/div>\n\n      <div class=\"ols-course-feature\">\n        <h3>Progress tracking<\/h3>\n        <p>\n          Identify strengths and weaknesses across atomic structure, isotopes, mass spectrometry, ionisation energies, electron configuration and periodic trends with targeted reporting.\n        <\/p>\n      <\/div>\n\n    <\/div>\n\n    <div class=\"ols-course-animation-wrap\">\n\n      <h3 class=\"ols-course-animation-title\">\n        See how the course works\n      <\/h3>\n\n      <div class=\"ols-animation-frame-shell\">\n        <iframe id=\"olsCourseAnimationFrame002\" title=\"OLS course preview animation\" loading=\"lazy\" referrerpolicy=\"no-referrer\">\n        <\/iframe>\n\n        <button 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<\/h1>\n        <\/div>\n      <\/div>\n\n      <section id=\"videoScene\" class=\"ols-video-scene\">\n        <div class=\"ols-video-scale-wrap\">\n          <div class=\"ols-video-card\">\n            <video id=\"lessonVideo\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Virtual-Lesson.mp4\" muted=\"\" playsinline=\"\" preload=\"auto\">\n            <\/video>\n          <\/div>\n        <\/div>\n      <\/section>\n    <\/div>\n  <\/section>\n\n  <section id=\"sceneMcq\" class=\"ols-scene\">\n    <div class=\"ols-mcq-stage\">\n      <div id=\"mcqIntroScreen\" class=\"ols-mcq-intro-screen\">\n        <div class=\"ols-mcq-intro-title-wrap\">\n          <h1 class=\"ols-mcq-intro-title\">\n            <span id=\"mcqIntroTitleText\"><\/span><span id=\"mcqIntroTitleCursor\" class=\"ols-title-cursor\"><\/span>\n          <\/h1>\n        <\/div>\n      <\/div>\n\n      <div class=\"ols-mcq-scale-wrap\">\n        <main id=\"mcqScreen\" class=\"ols-mcq-screen\">\n          <section class=\"mcq-question-area\">\n            <p class=\"mcq-question-lead\">Some successive ionisation energies for element X are shown.<\/p>\n\n            <table class=\"mcq-data-table\">\n              <thead>\n                <tr>\n                  <th>Ionisation energy<\/th>\n                  <th>Value \/ kJ mol<sup>\u22121<\/sup><\/th>\n                <\/tr>\n              <\/thead>\n              <tbody>\n                <tr><td>1st<\/td><td>738<\/td><\/tr>\n                <tr><td>2nd<\/td><td>1451<\/td><\/tr>\n                <tr><td>3rd<\/td><td>7733<\/td><\/tr>\n                <tr><td>4th<\/td><td>10543<\/td><\/tr>\n              <\/tbody>\n            <\/table>\n\n            <p class=\"mcq-question-main\">Which formula is most likely for the fluoride of element X?<\/p>\n\n            <div class=\"mcq-options-wrap\">\n              <div id=\"mcqWrongOption\" class=\"mcq-option-row\">\n                <span class=\"mcq-radio\"><\/span>\n                <span class=\"mcq-radio-ripple\"><\/span>\n                <span class=\"mcq-option-label\">XF<\/span>\n\n                <span id=\"mcqSpecificFeedback\" class=\"mcq-specific-feedback\">\n                  <span id=\"mcqCrossIcon\" class=\"mcq-cross-icon\">\u00d7<\/span>\n                  <span class=\"mcq-specific-feedback-text\">\n                    <span id=\"mcqSpecificText\"><\/span><span id=\"mcqSpecificCursor\" class=\"cursor mcq-specific-cursor\" style=\"display:none;\"><\/span>\n                  <\/span>\n                <\/span>\n              <\/div>\n\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">XF<sub>2<\/sub><\/span><\/div>\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">XF<sub>3<\/sub><\/span><\/div>\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">XF<sub>4<\/sub><\/span><\/div>\n            <\/div>\n\n            <button id=\"mcqSubmitButton\" class=\"mcq-submit-button\">Submit answer<\/button>\n          <\/section>\n\n          <section id=\"mcqGeneralFeedback\" class=\"mcq-general-feedback\">\n            <span id=\"mcqGeneralText\"><\/span><span id=\"mcqGeneralCursor\" class=\"cursor mcq-general-cursor\" style=\"display:none;\"><\/span>\n          <\/section>\n        <\/main>\n      <\/div>\n    <\/div>\n  <\/section>\n\n  <section id=\"sceneSaq\" class=\"ols-scene\">\n    <div class=\"ols-saq-stage\">\n      <div id=\"saqIntro\" class=\"ols-saq-intro\">\n        <div class=\"ols-saq-intro-title-wrap\">\n          <h1 class=\"ols-saq-intro-title\">\n            <span id=\"saqIntroTitleText\"><\/span><span id=\"saqIntroTitleCursor\" class=\"ols-title-cursor\"><\/span>\n          <\/h1>\n        <\/div>\n      <\/div>\n\n      <div class=\"ols-saq-scale-wrap\">\n        <main id=\"saqScreen\" class=\"ols-saq-screen\">\n          <section class=\"saq-question-area\">\n            <div class=\"saq-question-text\">\n              <strong>(ii)<\/strong>&nbsp;&nbsp; First ionisation energy generally increases across Period 3.<br>\n              Explain this trend in terms of nuclear charge, shielding and atomic radius.\n            <\/div>\n\n            <div class=\"saq-student-box\">\n              <span id=\"saqStudentText\"><\/span><span id=\"saqStudentCursor\" class=\"cursor\"><\/span>\n            <\/div>\n          <\/section>\n\n          <section id=\"saqTeacherFeedback\" class=\"saq-teacher-feedback\">\n            <span id=\"saqTeacherText\"><\/span><span id=\"saqTeacherCursor\" class=\"cursor saq-teacher-cursor\" style=\"display:none;\"><\/span>\n          <\/section>\n        <\/main>\n      <\/div>\n    <\/div>\n  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The outer electron is further from the nucleus and is shielded more strongly by inner shells, so the attraction to the nucleus is weaker.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why does atomic radius increase down a group?<\/h3>\n            <p>Atomic radius increases down a group because each element has an additional main electron shell. This places the outer electron further from the nucleus.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>What is shielding in ionisation energy?<\/h3>\n            <p>Shielding is the reduction in attraction between the nucleus and the outer electron due to repulsion from inner-shell electrons. More inner shells mean greater shielding.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why does increased nuclear charge not make ionisation energy increase down a group?<\/h3>\n            <p>Nuclear charge increases down a group because there are more protons. However, the extra occupied shells and increased shielding have a greater effect, so the outer electron is less strongly attracted overall.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>What wording should I use in an exam answer?<\/h3>\n            <p>Use this sequence: more occupied shells, larger atomic radius, more shielding, weaker attraction between the nucleus and the outer electron, less energy needed to remove the electron.<\/p>\n          <\/div>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-related-card\">\n        <h2>Related Topics<\/h2>\n        <p>Build the surrounding knowledge needed for ionisation energy, electronic structure and periodic trends.<\/p>\n        <div class=\"ols-related-grid\">\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/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-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/successive-ionisation-energy\/\">Successive Ionisation Energy<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/trends-in-a-period\/\">Trends in a Period<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/quantum-model\/\">Quantum Model<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/mass-spectrometry\/\">Mass Spectrometry<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Bonding &amp; Structure<\/a>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-attribution-card\">\n        <p><strong>Copyright notice:<\/strong> This OLS revision content, including the explanations, layout, diagrams, tables and embedded learning structure, is authored for Online Learning System by Dr. Mohammed Al-Fatah. It may not be copied, reproduced, redistributed or adapted without written permission.<\/p>\n      <\/section>\n\n      <script type=\"application\/ld+json\">\n{\n        \"@context\": \"https:\/\/schema.org\",\n        \"@graph\": [\n                {\n                        \"@type\": \"WebPage\",\n                        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/trends-in-a-group\/\",\n                        \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/trends-in-a-group\/\",\n                        \"name\": \"Trends in a Group - Ionisation Energy Revision Notes\",\n                        \"description\": \"A Level Chemistry revision notes on ionisation energy trends down a group, including atomic radius, shielding, nuclear charge and exam wording.\",\n                        \"inLanguage\": \"en-GB\",\n                        \"isPartOf\": {\n                                \"@type\": \"WebSite\",\n                                \"name\": \"Online Learning System\",\n                                \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/\"\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                        \"about\": [\n                                { \"@type\": \"Thing\", \"name\": \"Ionisation energy\" },\n                                { \"@type\": \"Thing\", \"name\": \"Periodic trends\" },\n                                { \"@type\": \"Thing\", \"name\": \"Atomic radius\" },\n                                { \"@type\": \"Thing\", \"name\": \"Shielding\" }\n                        ]\n                },\n                {\n                        \"@type\": \"BreadcrumbList\",\n                        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/trends-in-a-group\/#breadcrumb\",\n                        \"itemListElement\": [\n                                { \"@type\": \"ListItem\", \"position\": 1, \"name\": \"Revision Notes\", \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\" },\n                                { \"@type\": \"ListItem\", \"position\": 2, \"name\": \"A Level Chemistry\", \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\" },\n                                { \"@type\": \"ListItem\", \"position\": 3, \"name\": \"Edexcel International\", \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\" },\n                                { \"@type\": \"ListItem\", \"position\": 4, \"name\": \"Topic 2 Atomic Structure & The Periodic Table\", \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/\" },\n                                { \"@type\": \"ListItem\", \"position\": 5, \"name\": \"Ionisation Energy\", \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/\" },\n                                { \"@type\": \"ListItem\", \"position\": 6, \"name\": \"Trends in a Group\", \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/trends-in-a-group\/\" }\n                        ]\n                },\n                {\n                        \"@type\": \"Course\",\n                        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-2-atomic-structure-and-the-periodic-table\/ionisation-energy\/trends-in-a-group\/#course\",\n                        \"name\": \"Trends in a Group - 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