{"id":7806,"date":"2026-09-13T19:08:53","date_gmt":"2026-09-13T18:08:53","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/ionic-bonding\/polarisation-of-ions\/"},"modified":"2026-09-26T10:25:35","modified_gmt":"2026-09-26T09:25:35","slug":"polarisation-of-ions","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/ionic-bonding\/polarisation-of-ions\/","title":{"rendered":"Polarisation of Ions"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-polarisation-of-ions-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      --grey-text: #667085;\n      --body-text: #1f2937;\n      --border: rgba(28, 36, 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class=\"ols-sidebar\">\n  <div class=\"ols-sidebar-header\">\n    <h3>Revision Notes<\/h3>\n    <p>Cambridge International AS Level Chemistry<\/p>\n  <\/div>\n  <div class=\"ols-topic-group\">\n    <h4>3.2 Ionic Bonding<\/h4>\n    <ul class=\"ols-topic-list\">\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/ionic-bonding\/\">Part overview<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/ionic-bonding\/nature-of-ionic-bonding\/\">Nature of Ionic Bonding<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/ionic-bonding\/polarisation-of-ions\/\">Polarisation of Ions<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/ionic-bonding\/physical-properties-of-ionic-compounds\/\">Physical Properties of Ionic Compounds<\/a><\/li>\n    <\/ul>\n  <\/div>\n  <div class=\"ols-topic-group\">\n    <h4>Other Topic 3 Parts<\/h4>\n    <ul class=\"ols-topic-list\">\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/\">Topic 3 overview<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/electronegativity\/\">3.1 Electronegativity<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/metallic-bonding\/\">3.3 Metallic Bonding<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/\">3.4 Covalent Bonding<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/shapes-of-molecules\/\">3.5 Shapes of Molecules<\/a><\/li>\n    <\/ul>\n  <\/div>\n  <div class=\"ols-topic-group\">\n    <h4>Related<\/h4>\n    <ul class=\"ols-topic-list\">\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-4-states-of-matter\/structure-types\/\">Topic 4: Structure Types<\/a><\/li>\n    <\/ul>\n  <\/div>\n<\/aside>\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 = 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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\/cie\/\">Cambridge International (CIE)<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/\">Topic 3 Chemical Bonding<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/ionic-bonding\/\">3.2 Ionic Bonding<\/a> \/\n<span>Polarisation of Ions<\/span>\n<\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Polarisation of Ions<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to polarisation, polarising power, anion polarisability and covalent character for Cambridge International AS &amp; A Level Chemistry.<\/p>\n\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">AS Level<\/div>\n<div class=\"ols-badge\">Topic 3: Chemical Bonding<\/div>\n<div class=\"ols-badge\">9701 Papers 1 and 2<\/div>\n        <\/div>\n\n        <div class=\"ols-author\">\n\n    <img decoding=\"async\"\n      class=\"ols-author-avatar-img\"\n      src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\"\n      alt=\"Dr. Mohammed Al-Fatah\"\n    >\n\n    <div class=\"ols-author-content\">\n\n      <h2 class=\"ols-author-title\">\n        Written by: Dr. Mohammed Al-Fatah\n      <\/h2>\n\n      <p class=\"ols-author-description\">\n        Chemistry specialist revision notes for A Level Chemistry.\n      <\/p>\n\n      <a class=\"ols-linkedin-pill\" href=\"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\" target=\"_blank\" rel=\"noopener noreferrer\">\n\n        <svg class=\"ols-linkedin-icon\" viewBox=\"0 0 24 24\" fill=\"currentColor\" aria-hidden=\"true\">\n          <path d=\"M4.98 3.5C4.98 4.88 3.86 6 2.48 6S0 4.88 0 3.5 1.12 1 2.48 1s2.5 1.12 2.5 2.5zM.5 8h4V24h-4V8zm7 0h3.8v2.2h.1c.5-.9 1.8-2.2 3.9-2.2 4.2 0 5 2.8 5 6.4V24h-4v-7.6c0-1.8 0-4.2-2.6-4.2s-3 2-3 4v7.8h-4V8z\"\/>\n        <\/svg>\n\n        View LinkedIn Profile\n\n      <\/a>\n\n    <\/div>\n\n  <\/div>\n      <\/header>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">1<\/div>\n          <h2>What Is Polarisation?<\/h2>\n        <\/div>\n\n        <p><strong>Polarisation<\/strong> occurs when a positive ion, called a <strong>cation<\/strong>, attracts and distorts the electron cloud of a negative ion, called an <strong>anion<\/strong>.<\/p>\n        <p>The anion is not pulled apart into separate particles. Instead, its electron cloud becomes unevenly distributed because the electrons are attracted towards the cation.<\/p>\n        <p>This distortion gives the bond more <strong>covalent character<\/strong>, because electron density is drawn between the two ions instead of being held as a completely separate spherical anion cloud.<\/p>\n\n        <div class=\"ols-definition-box\">\n          <p><strong>Definition:<\/strong> Polarising power is the ability of a cation to distort an anion. Polarisability is the ease with which an anion is distorted.<\/p>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Key idea:<\/strong> Polarisation explains why bonding is not always purely ionic or purely covalent. Many compounds lie on a bonding continuum between the two extremes.<\/p>\n        <\/div>\n\n        <div class=\"ols-zoom-card wide\">\n          <div class=\"ols-zoom-card-image\">\n            <img decoding=\"async\" class=\"ols-zoomable-img ols-lightbox-target\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/wave-50.jpg\" alt=\"Four-panel ionic to covalent continuum, NaCl to SiCl4, with the cation always navy and the anion always teal and the clouds merging more at each step\">\n          <\/div>\n          <div class=\"ols-zoom-card-caption\">\n            <p>Increasing polarisation changes the electron distribution between ions, so the bonding gains more covalent character.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Which Ion Is Distorted?<\/h2>\n<p>Apply the idea of polarisation to a compound this page has not described.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-601\" class=\"h5p-iframe\" data-content-id=\"601\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Polarisation MCQ: Which Electron Cloud Is Distorted in Lithium Iodide?\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">2<\/div>\n          <h2>Cation Polarising Power<\/h2>\n        <\/div>\n\n        <p>The ability of a cation to polarise an anion depends on its <strong>charge density<\/strong>. Charge density means charge relative to size.<\/p>\n        <p>A cation has greater polarising power when it has a <strong>higher positive charge<\/strong> or a <strong>smaller ionic radius<\/strong>. Both factors concentrate positive charge into a smaller volume.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Factor<\/th>\n                <th>Effect on polarising power<\/th>\n                <th>Example<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Factor\">Higher cation charge<\/td>\n                <td data-label=\"Effect on polarising power\">Increases attraction for the anion&#8217;s electrons, so the anion electron cloud is distorted more strongly.<\/td>\n                <td data-label=\"Example\">Mg<sup>2+<\/sup> has greater polarising power than Na<sup>+<\/sup> because Mg<sup>2+<\/sup> has a higher positive charge.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Factor\">Smaller cation radius<\/td>\n                <td data-label=\"Effect on polarising power\">Increases charge density because the positive charge is concentrated into a smaller volume.<\/td>\n                <td data-label=\"Example\">Li<sup>+<\/sup> has greater polarising power than Cs<sup>+<\/sup> because Li<sup>+<\/sup> is much smaller.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Factor\">Charge-to-radius ratio<\/td>\n                <td data-label=\"Effect on polarising power\">A cation with a larger charge-to-radius ratio has stronger polarising power.<\/td>\n                <td data-label=\"Example\">Ca<sup>2+<\/sup> has greater polarising power than Li<sup>+<\/sup> because its higher charge outweighs its larger size.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Typical polarising power order:<\/strong> Cs<sup>+<\/sup> &lt; Na<sup>+<\/sup> &lt; Li<sup>+<\/sup> &lt; Ca<sup>2+<\/sup> &lt; Mg<sup>2+<\/sup> &lt; Al<sup>3+<\/sup>.<\/p>\n        <\/div>\n      <\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: The More Polarising Cation<\/h2>\n<p>In each of five pairs, click the cation with the greater polarising power.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-157\" class=\"h5p-iframe\" data-content-id=\"157\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Polarisation Mark the Words: The More Polarising Cation in Each Pair\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">3<\/div>\n          <h2>Anion Polarisability<\/h2>\n        <\/div>\n\n        <p>The ease with which an anion is polarised also depends on charge density. Anions are more easily polarised when their electron clouds are easier to distort.<\/p>\n        <p>A larger anion is more polarisable because its outer electrons are further from the nucleus and are held less strongly. An anion with a higher negative charge is also more polarisable because electron-electron repulsion is greater.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Factor<\/th>\n                <th>Effect on polarisability<\/th>\n                <th>Example<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Factor\">Higher negative charge<\/td>\n                <td data-label=\"Effect on polarisability\">Extra negative charge increases electron-electron repulsion, making the electron cloud easier to distort.<\/td>\n                <td data-label=\"Example\">O<sup>2-<\/sup> is more easily polarised than F<sup>&#8211;<\/sup>.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Factor\">Larger anion radius<\/td>\n                <td data-label=\"Effect on polarisability\">The outer electrons are further from the nucleus and are held less strongly.<\/td>\n                <td data-label=\"Example\">I<sup>&#8211;<\/sup> is more easily polarised than Cl<sup>&#8211;<\/sup> because I<sup>&#8211;<\/sup> is much larger.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Typical halide polarisability order:<\/strong> F<sup>&#8211;<\/sup> &lt; Cl<sup>&#8211;<\/sup> &lt; Br<sup>&#8211;<\/sup> &lt; I<sup>&#8211;<\/sup>.<\/p>\n        <\/div>\n      <\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: The Most Polarisable Anion<\/h2>\n<p>Use both size and charge to choose between four anions.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-158\" class=\"h5p-iframe\" data-content-id=\"158\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Polarisation MCQ: The Most Polarisable of Four Anions\"><\/iframe><\/div><\/div>\n<\/section>\n\n<!-- 3D card: anion-polarisation (swapped 26 Sep 2026) -->\n<section class=\"ols-pol-001\" id=\"olsPol001\">\n<style>\n@import url('https:\/\/fonts.googleapis.com\/css2?family=Poppins:wght@300;400;500;600&display=swap');\n\n.ols-pol-001{\n  font-family:'Poppins',system-ui,-apple-system,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;\n  color:#1C244B; 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padding:1px 5px;}\n  .ols-pol-001 .pol-lab.l-cmp{font-size:11.5px; padding:3px 8px;}\n  .ols-pol-001 .pol-caption{font-size:10.5px; padding:5px 9px; max-width:64%;}\n  .ols-pol-001 .pol-badge{font-size:10.5px; padding:4px 9px;}\n  .ols-pol-001 .pol-badge.b-shape{font-size:12px;}\n  .ols-pol-001 .pol-badges{max-width:70%;}\n  .ols-pol-001 .pol-info{padding:18px;}\n}\n@media (prefers-reduced-motion:reduce){\n  .ols-pol-001 .pol-seg button,.ols-pol-001 .pol-pill{transition:none;}\n}\n\n.ols-cc-pol-001{\n  font-family:'Poppins',system-ui,-apple-system,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;\n  margin:10px auto 0; text-align:center; font-size:11px; font-style:italic; color:#aab0c0;\n}\n.ols-cc-pol-001 a{color:#aab0c0; text-decoration:none;}\n.ols-cc-pol-001 a:hover{text-decoration:underline;}\n<\/style>\n\n<div class=\"pol-head\">\n  <h2 class=\"pol-title\">Polarisation of Anions: AlCl<sub>3<\/sub> and AlF<sub>3<\/sub><\/h2>\n  <p class=\"pol-sub\">See how the small, highly charged Al<sup>3+<\/sup> ion pulls on the electron clouds of the anions around it, distorting large Cl<sup>&minus;<\/sup> far more than small F<sup>&minus;<\/sup>.<\/p>\n<\/div>\n\n<div class=\"pol-stage\" id=\"polStage\">\n  <canvas class=\"pol-canvas\" id=\"polCanvas\"><\/canvas>\n  <div class=\"pol-overlay\" id=\"polOverlay\"><\/div>\n  <div class=\"pol-caption\" id=\"polCaption\"><\/div>\n  <div class=\"pol-hint\" id=\"polHint\">Drag to rotate<\/div>\n<\/div>\n\n<div class=\"pol-controls\">\n  <div class=\"pol-row\">\n    <span class=\"pol-rowlab\">Compound<\/span>\n    <div class=\"pol-seg\" role=\"group\" aria-label=\"Compound\">\n      <button type=\"button\" data-c=\"AlCl3\" aria-pressed=\"true\">Aluminium chloride, AlCl<sub>3<\/sub><\/button>\n      <button type=\"button\" data-c=\"AlF3\" aria-pressed=\"false\">Aluminium fluoride, AlF<sub>3<\/sub><\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"pol-row\">\n    <span class=\"pol-rowlab\">Step<\/span>\n    <div class=\"pol-seg\" role=\"group\" aria-label=\"Step\">\n      <button type=\"button\" data-step=\"1\" aria-pressed=\"true\">Ions<\/button>\n      <button type=\"button\" data-step=\"2\" aria-pressed=\"false\">Polarise<\/button>\n      <button type=\"button\" data-step=\"3\" aria-pressed=\"false\">Compare<\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"pol-row\">\n    <span class=\"pol-rowlab\">View<\/span>\n    <div class=\"pol-seg\" role=\"group\" aria-label=\"Camera view\">\n      <button type=\"button\" data-v=\"front\" aria-pressed=\"false\">Front<\/button>\n      <button type=\"button\" data-v=\"side\" aria-pressed=\"false\">Side<\/button>\n      <button type=\"button\" data-v=\"top\" aria-pressed=\"false\">Top<\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"pol-row\">\n    <span class=\"pol-rowlab\">Show<\/span>\n    <button type=\"button\" class=\"pol-pill\" id=\"polTogNorm\" aria-pressed=\"false\"><i class=\"dot\"><\/i>Normal clouds<\/button>\n    <button type=\"button\" class=\"pol-pill\" id=\"polTogChg\" aria-pressed=\"true\"><i class=\"dot\"><\/i>Charge labels<\/button>\n    <button type=\"button\" class=\"pol-pill\" id=\"polTogRul\" aria-pressed=\"false\"><i class=\"dot\"><\/i>Ionic radii rulers<\/button>\n  <\/div>\n\n  <div class=\"pol-row\">\n    <span class=\"pol-rowlab\">Motion<\/span>\n    <button type=\"button\" class=\"pol-pill\" id=\"polSpin\" aria-pressed=\"false\"><i class=\"dot\"><\/i>Rotation<\/button>\n    <button type=\"button\" class=\"pol-pill\" id=\"polResetV\">Reset view<\/button>\n  <\/div>\n<\/div>\n\n<div class=\"pol-info\">\n  <h3 id=\"polInfoTitle\"><\/h3>\n  <p id=\"polInfoText\"><\/p>\n  <div class=\"pol-facts\" id=\"polFacts\"><\/div>\n  <div class=\"pol-key\">\n    <span><i style=\"background:#787e8c\"><\/i>Al<sup>3+<\/sup><\/span>\n    <span><i style=\"background:#3aa048\"><\/i>Cl<sup>&minus;<\/sup><\/span>\n    <span><i style=\"background:#96cd7a\"><\/i>F<sup>&minus;<\/sup><\/span>\n    <span><i style=\"background:rgba(40,128,56,0.35); border:1.5px dotted rgba(40,128,56,0.9)\"><\/i>Electron density<\/span>\n    <span><i style=\"background:#ffffff; border:1.5px dashed rgba(28,36,75,0.6)\"><\/i>Normal cloud<\/span>\n    <span><i style=\"background:#1C244B\"><\/i>Ionic radius ruler<\/span>\n  <\/div>\n<\/div>\n<\/section>\n\n<p class=\"ols-cc-pol-001\">&copy; Dr. Mohammed Al-Fatah &#8211; <a href=\"https:\/\/www.onlinelearningsystem.net\" target=\"_blank\" rel=\"noopener\">onlinelearningsystem.net<\/a><\/p>\n\n<script src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/JS\/anion-polarisation.js?v=20260926\"><\/script>\n\n      <article class=\"ols-note-card orange\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">4<\/div>\n          <h2>Polarisation and Covalent Character<\/h2>\n        <\/div>\n\n        <p>When polarisation is weak, the compound is closer to the ionic end of the bonding continuum. When polarisation is strong, the anion electron cloud is pulled towards the cation and the compound gains more covalent character.<\/p>\n        <p>Small, highly charged cations such as <strong>Al<sup>3+<\/sup><\/strong> and <strong>Si<sup>4+<\/sup><\/strong> can strongly distort the electron cloud of chloride ions. This is why aluminium chloride and silicon chloride bonding is more covalent than simple sodium chloride bonding.<\/p>\n\n        <div class=\"ols-rule-list\">\n          <div class=\"ols-rule-item\">\n            <h3>More ionic character<\/h3>\n            <p>Large or low-charge cations combined with small, low-polarisability anions tend to show more ionic character.<\/p>\n          <\/div>\n\n          <div class=\"ols-rule-item\">\n            <h3>More covalent character<\/h3>\n            <p>Small, highly charged cations combined with large, polarisable anions tend to show more covalent character.<\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-zoom-card wide\">\n          <div class=\"ols-figure-card\">\n<div class=\"ols-figure-image\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/fix-20.jpg\" alt=\"Aluminium halides from AlF\u2083 to AlI\u2083: the halide ion gets larger and more polarisable, so Al\u00b3\u207a distorts it more and covalent character increases.\"><\/div>\n<div class=\"ols-figure-caption\"><p>Bonding in aluminium halides showing increasing anion polarisation<\/p><\/div>\n<\/div>\n          <div class=\"ols-zoom-card-caption\">\n            <p>A highly charged Al<sup>3+<\/sup> ion distorts larger halide ions more strongly, increasing covalent character.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Rank the Covalent Character<\/h2>\n<p>Put five compounds in order from most ionic to most covalent character.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-159\" class=\"h5p-iframe\" data-content-id=\"159\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Polarisation Sort: Most Ionic to Most Covalent Character\"><\/iframe><\/div><\/div>\n<\/section>\n\n\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">5<\/div>\n          <h2>How Polarisation Links to Ionic Bond Strength<\/h2>\n        <\/div>\n\n        <p>Ionic bond strength is affected by the electrostatic attraction between oppositely charged ions. Higher ionic charge and smaller ionic radius usually produce stronger attractions and higher melting points.<\/p>\n        <p>Polarisation adds another layer of explanation. If the cation strongly distorts the anion, the bonding may gain covalent character instead of behaving like a simple ionic lattice.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Comparison<\/th>\n                <th>Main reason<\/th>\n                <th>Typical consequence<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Comparison\">NaF compared with CaO<\/td>\n                <td data-label=\"Main reason\">CaO contains Ca<sup>2+<\/sup> and O<sup>2-<\/sup>, so the ionic charges are larger.<\/td>\n                <td data-label=\"Typical consequence\">Stronger electrostatic attraction and a much higher melting point.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Comparison\">NaF compared with CsF<\/td>\n                <td data-label=\"Main reason\">Na<sup>+<\/sup> is smaller than Cs<sup>+<\/sup>, so Na<sup>+<\/sup> and F<sup>&#8211;<\/sup> ions can sit closer together.<\/td>\n                <td data-label=\"Typical consequence\">Stronger electrostatic attraction in NaF than in CsF.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Comparison\">NaCl compared with AlCl<sub>3<\/sub><\/td>\n                <td data-label=\"Main reason\">Al<sup>3+<\/sup> is small and highly charged, so it strongly polarises Cl<sup>&#8211;<\/sup>.<\/td>\n                <td data-label=\"Typical consequence\">AlCl<sub>3<\/sub> shows greater covalent character than NaCl.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n      <\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Which Reason Applies?<\/h2>\n<p>In each round, pick the one statement with the correct comparison and the correct reason.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-156\" class=\"h5p-iframe\" data-content-id=\"156\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Polarisation Summary: Charge, Radius or Polarisation?\"><\/iframe><\/div><\/div>\n<\/section>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Explain a Group 2 Contrast<\/h2>\n<p>Write a short explanation, then compare it with the mark points and the model answer.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-602\" class=\"h5p-iframe\" data-content-id=\"602\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Polarisation Explain: Beryllium Chloride Compared with Barium Chloride\"><\/iframe><\/div><\/div>\n<\/section>\n\n      \n\n      <section class=\"ols-faq-card ols-quicksnap-card\">\n        <h2>QuickSnap<\/h2>\n        <div class=\"ols-faq-list\">\n          <div class=\"ols-faq-item\">\n            <h3>1. Polarisation<\/h3>\n            <p>Polarisation is the distortion of an anion&#8217;s electron cloud by a nearby cation. The more the electron cloud is distorted, the more covalent character the bonding can show.<\/p>\n          <\/div>\n\n          <div class=\"ols-faq-item\">\n            <h3>2. Cation polarising power<\/h3>\n            <p>Small, highly charged cations have high charge density and strong polarising power. Al<sup>3+<\/sup> is strongly polarising because it is small and has a 3+ charge.<\/p>\n          <\/div>\n\n          <div class=\"ols-faq-item\">\n            <h3>3. Anion polarisability<\/h3>\n            <p>Large anions and anions with higher negative charge are more easily polarised because their outer electron clouds are held less strongly.<\/p>\n          <\/div>\n\n          <div class=\"ols-faq-item\">\n            <h3>4. Aluminium halide comparison<\/h3>\n            <p>F<sup>&#8211;<\/sup> is small and difficult to polarise, so AlF<sub>3<\/sub> is more ionic. Cl<sup>&#8211;<\/sup> is larger and more polarisable, so AlCl<sub>3<\/sub> shows greater covalent character.<\/p>\n          <\/div>\n\n          <div class=\"ols-faq-item\">\n            <h3>5. 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opacity: 0;\r\n      visibility: hidden;\r\n      pointer-events: none;\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-animation-start-content {\r\n      position: relative;\r\n      z-index: 2;\r\n      display: grid;\r\n      justify-items: center;\r\n      gap: 16px;\r\n      padding: 24px;\r\n      text-align: center;\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-animation-play-circle {\r\n      width: 96px;\r\n      height: 96px;\r\n      border-radius: 50%;\r\n      background: #ffffff;\r\n      color: var(--navy);\r\n      display: flex;\r\n      align-items: center;\r\n      justify-content: center;\r\n      box-shadow:\r\n        0 18px 40px rgba(28, 36, 75, 0.30),\r\n        0 0 0 12px rgba(255, 255, 255, 0.22);\r\n      animation: olsAnimationPlayPulse001 1.8s ease-in-out infinite;\r\n      transition:\r\n        transform 0.25s ease,\r\n        background 0.25s ease,\r\n        color 0.25s ease;\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-animation-start-overlay:hover .ols-animation-play-circle {\r\n      transform: scale(1.08);\r\n      background: var(--navy);\r\n      color: #ffffff;\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-animation-play-icon {\r\n      width: 0;\r\n      height: 0;\r\n      margin-left: 7px;\r\n      border-top: 18px solid transparent;\r\n      border-bottom: 18px solid transparent;\r\n      border-left: 28px solid currentColor;\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-animation-start-text {\r\n      max-width: 540px;\r\n      margin: 0;\r\n      color: #ffffff;\r\n      font-size: clamp(20px, 3vw, 32px);\r\n      line-height: 1.2;\r\n      font-weight: 800;\r\n      text-shadow: 0 8px 20px rgba(0, 0, 0, 0.28);\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-animation-pause-button {\r\n      position: absolute;\r\n      left: 16px;\r\n      bottom: 16px;\r\n      z-index: 7;\r\n      display: none;\r\n      align-items: center;\r\n      justify-content: center;\r\n      min-width: 92px;\r\n      padding: 10px 16px;\r\n      border: 0;\r\n      border-radius: 999px;\r\n      background: rgba(28, 36, 75, 0.92);\r\n      color: #ffffff;\r\n      font-family: Poppins, Arial, sans-serif;\r\n      font-size: 14px;\r\n      line-height: 1.2;\r\n      font-weight: 800;\r\n      cursor: pointer;\r\n      box-shadow: 0 12px 28px rgba(28, 36, 75, 0.24);\r\n      transition:\r\n        transform 0.2s ease,\r\n        background 0.2s ease,\r\n        box-shadow 0.2s ease;\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-animation-pause-button:hover {\r\n      transform: translateY(-2px);\r\n      background: var(--blue);\r\n      box-shadow: 0 16px 34px rgba(37, 99, 235, 0.28);\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-animation-pause-button.is-visible {\r\n      display: inline-flex;\r\n    }\r\n\r\n    @keyframes olsAnimationPlayPulse001 {\r\n      0% {\r\n        box-shadow:\r\n          0 18px 40px rgba(28, 36, 75, 0.30),\r\n          0 0 0 0 rgba(255, 255, 255, 0.40);\r\n      }\r\n\r\n      70% {\r\n        box-shadow:\r\n          0 18px 40px rgba(28, 36, 75, 0.30),\r\n          0 0 0 18px rgba(255, 255, 255, 0);\r\n      }\r\n\r\n      100% {\r\n        box-shadow:\r\n          0 18px 40px rgba(28, 36, 75, 0.30),\r\n          0 0 0 0 rgba(255, 255, 255, 0);\r\n      }\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-course-video-status {\r\n      margin: 14px 0 0;\r\n      text-align: center;\r\n      color: var(--grey-text);\r\n      font-size: 13px;\r\n      line-height: 1.5;\r\n      font-weight: 500;\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-course-cta-bottom {\r\n      display: flex;\r\n      justify-content: center;\r\n      padding-top: 22px;\r\n      border-top: 1px solid var(--border);\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-course-button {\r\n      display: inline-flex;\r\n      align-items: center;\r\n      justify-content: center;\r\n      padding: 15px 28px;\r\n      border-radius: 999px;\r\n      background: var(--navy);\r\n      color: #ffffff;\r\n      text-decoration: none;\r\n      font-size: 16px;\r\n      line-height: 1.2;\r\n      font-weight: 800;\r\n      box-shadow: 0 12px 26px rgba(28, 36, 75, 0.18);\r\n      transition:\r\n        transform 0.2s ease,\r\n        background 0.2s ease,\r\n        box-shadow 0.2s ease;\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-course-button:hover {\r\n      transform: translateY(-2px);\r\n      background: var(--blue);\r\n      color: #ffffff;\r\n      box-shadow: 0 16px 32px rgba(37, 99, 235, 0.24);\r\n    }\r\n\r\n    .ols-course-cta-ionic .ols-course-button-top {\r\n      flex-shrink: 0;\r\n      padding: 12px 22px;\r\n      font-size: 15px;\r\n    }\r\n\r\n    @media (max-width: 900px) {\r\n      .ols-course-cta-ionic .ols-course-cta-top {\r\n        grid-template-columns: 1fr;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-course-cta-image-link {\r\n        max-width: 520px;\r\n        margin: 0 auto;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-course-cta-intro-stats {\r\n        grid-template-columns: 1fr;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-animation-frame-shell {\r\n        height: 520px;\r\n      }\r\n    }\r\n\r\n    @media (max-width: 760px) {\r\n      .ols-course-cta-ionic {\r\n        margin: 26px 0 22px;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-course-cta-card {\r\n        padding: 20px;\r\n        border-radius: 24px;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-course-cta-header-row {\r\n        align-items: stretch;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-course-button-top {\r\n        width: 100%;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-course-cta-stats,\r\n      .ols-course-cta-ionic .ols-course-cta-features {\r\n        grid-template-columns: 1fr;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-course-animation-wrap {\r\n        padding: 0;\r\n        border-radius: 0;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-animation-frame-shell {\r\n        height: 420px;\r\n        border-radius: 18px;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-animation-play-circle {\r\n        width: 76px;\r\n        height: 76px;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-animation-play-icon {\r\n        border-top-width: 14px;\r\n        border-bottom-width: 14px;\r\n        border-left-width: 22px;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-animation-pause-button {\r\n        left: 12px;\r\n        bottom: 12px;\r\n        min-width: 84px;\r\n        padding: 9px 14px;\r\n        font-size: 13px;\r\n      }\r\n\r\n      .ols-course-cta-ionic .ols-course-button {\r\n        width: 100%;\r\n      }\r\n    }\r\n  <\/style>\r\n\r\n  <div class=\"ols-course-cta-card\">\r\n\r\n    <div class=\"ols-course-cta-top\">\r\n\r\n      <a class=\"ols-course-cta-image-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/ionic-and-metallic-bonding-topic-3-cambridge-international\/\" aria-label=\"Open the Cambridge International AS and A Level Chemistry Topic 3 Ionic and Metallic Bonding course page\">\r\n\r\n        <div class=\"ols-course-cta-image\">\r\n          <img decoding=\"async\"\r\n            src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/cambridge-international-a-level-chemistry-topic-3-ionic-metallic-bonding-interactive-course-banner.jpg\"\r\n            alt=\"Cambridge International AS and A Level Chemistry Topic 3 Ionic and Metallic Bonding interactive course banner\"\r\n          >\r\n        <\/div>\r\n\r\n      <\/a>\r\n\r\n      <div class=\"ols-course-cta-content\">\r\n\r\n        <div class=\"ols-course-cta-header-row\">\r\n\r\n          <div class=\"ols-course-cta-kicker\">\r\n            Cambridge 9701 | Topic 3 Course\r\n          <\/div>\r\n\r\n          <a class=\"ols-course-button ols-course-button-top\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/ionic-and-metallic-bonding-topic-3-cambridge-international\/\">\r\n            View Course\r\n          <\/a>\r\n\r\n        <\/div>\r\n\r\n        <h2>\r\n          Master Ionic and Metallic Bonding for Cambridge International AS &amp; A Level Chemistry\r\n        <\/h2>\r\n\r\n      <\/div>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-cta-intro-stats\">\r\n\r\n      <p class=\"ols-course-cta-intro\">\r\n        Continue from these free revision notes into the full Topic 3 Ionic and Metallic Bonding course. The guided video lessons are ready now; the Cambridge International MCQ bank, teacher-marked short-answer questions and KASP spec-point report are being written, and the course opens for enrolment as soon as they are complete.\r\n      <\/p>\r\n\r\n      <div class=\"ols-course-cta-stats\">\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>Recorded lessons<\/span>\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>Video lessons<\/span>\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>MCQ practice<\/span>\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>SAQ practice<\/span>\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n      <\/div>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-cta-features\">\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Guided video teaching<\/h3>\r\n        <p>\r\n          Learn the chemistry and exam technique through structured video lessons with worked examples and walkthroughs.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Instant MCQ feedback<\/h3>\r\n        <p>\r\n          Auto-marked MCQ quizzes provide immediate diagnostic feedback for every answer choice.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Teacher-marked SAQs<\/h3>\r\n        <p>\r\n          Submit written exam responses and receive chemistry specialist feedback with improvement guidance.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Progress tracking<\/h3>\r\n        <p>\r\n          Identify strengths and weaknesses across the full Topic 3 specification with targeted reporting.\r\n        <\/p>\r\n      <\/div>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-animation-wrap\">\r\n\r\n      <h3 class=\"ols-course-animation-title\">\r\n        See how the course works\r\n      <\/h3>\r\n\r\n      <div class=\"ols-animation-frame-shell\">\r\n        <iframe\r\n          id=\"olsCourseAnimationFrame001\"\r\n          title=\"OLS course preview animation\"\r\n          loading=\"lazy\"\r\n          referrerpolicy=\"no-referrer\">\r\n        <\/iframe>\r\n\r\n        <button\r\n          class=\"ols-animation-start-overlay\"\r\n          id=\"olsCourseAnimationStart001\"\r\n          type=\"button\"\r\n          aria-label=\"Play OLS course preview animation\">\r\n          <span class=\"ols-animation-start-content\">\r\n            <span class=\"ols-animation-play-circle\" aria-hidden=\"true\">\r\n              <span class=\"ols-animation-play-icon\"><\/span>\r\n            <\/span>\r\n            <span class=\"ols-animation-start-text\">\r\n              Play course preview animation\r\n            <\/span>\r\n          <\/span>\r\n        <\/button>\r\n\r\n        <button\r\n          class=\"ols-animation-pause-button\"\r\n          id=\"olsCourseAnimationPause001\"\r\n          type=\"button\"\r\n          aria-label=\"Pause course preview animation\">\r\n          Pause\r\n        <\/button>\r\n      <\/div>\r\n\r\n      <p class=\"ols-course-video-status\">\r\n        Click play to start the course preview animation.\r\n      <\/p>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-cta-bottom\">\r\n\r\n      <a class=\"ols-course-button\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/ionic-and-metallic-bonding-topic-3-cambridge-international\/\">\r\n        View Ionic and Metallic Bonding Course\r\n      <\/a>\r\n\r\n    <\/div>\r\n\r\n  <\/div>\r\n\r\n  <template id=\"olsCourseAnimationTemplate001\">\r\n<!DOCTYPE html>\r\n<html lang=\"en\">\r\n<head>\r\n<meta charset=\"UTF-8\">\r\n<meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">\r\n<title>OLS Combined Promo Animation<\/title>\r\n\r\n<style>\r\n*{box-sizing:border-box;}\r\n\r\nhtml.ols-animation-paused *,\r\nhtml.ols-animation-paused *::before,\r\nhtml.ols-animation-paused *::after{\r\n  animation-play-state:paused!important;\r\n}\r\n\r\n:root{\r\n  --ols-video-screen-w:1180;\r\n  --ols-video-screen-h:664;\r\n  --ols-video-screen-scale:1;\r\n  --ols-mcq-screen-w:1360;\r\n  --ols-mcq-screen-h:1130;\r\n  --ols-mcq-screen-scale:1;\r\n  --ols-saq-screen-w:1360;\r\n  --ols-saq-screen-h:965;\r\n  --ols-saq-screen-scale:1;\r\n}\r\n\r\nhtml,\r\nbody{\r\n  width:100%;\r\n  height:100%;\r\n}\r\n\r\nbody{\r\n  margin:0;\r\n  overflow:hidden;\r\n  font-family:Poppins,Arial,sans-serif;\r\n  background:#e9efff;\r\n}\r\n\r\n.ols-combined-stage{\r\n  position:relative;\r\n  width:100vw;\r\n  height:100vh;\r\n  overflow:hidden;\r\n  background:\r\n    radial-gradient(circle at top left,rgba(70,127,247,0.14),transparent 34%),\r\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\r\n}\r\n\r\n.ols-scene{\r\n  position:absolute;\r\n  inset:0;\r\n  width:100vw;\r\n  height:100vh;\r\n  opacity:0;\r\n  visibility:hidden;\r\n  pointer-events:none;\r\n}\r\n\r\n.ols-scene.active{\r\n  opacity:1;\r\n  visibility:visible;\r\n  pointer-events:auto;\r\n}\r\n\r\n.ols-scene.fade-out{\r\n  animation:olsSceneFadeOut 0.85s ease forwards;\r\n}\r\n\r\n@keyframes olsSceneFadeOut{\r\n  to{\r\n    opacity:0;\r\n    visibility:hidden;\r\n  }\r\n}\r\n\r\n.ols-title-cursor{\r\n  display:inline-block;\r\n  width:5px;\r\n  height:0.85em;\r\n  background:#1C244B;\r\n  margin-left:8px;\r\n  transform:translateY(8px);\r\n  animation:olsBlink 0.8s infinite;\r\n}\r\n\r\n.cursor{\r\n  display:inline-block;\r\n  width:3px;\r\n  height:28px;\r\n  background:#1c244b;\r\n  margin-left:3px;\r\n  transform:translateY(5px);\r\n  animation:olsBlink 0.8s infinite;\r\n}\r\n\r\n@keyframes olsBlink{\r\n  0%,45%{opacity:1;}\r\n  46%,100%{opacity:0;}\r\n}\r\n\r\n.ols-video-stage,\r\n.ols-mcq-stage,\r\n.ols-saq-stage{\r\n  width:100vw;\r\n  height:100vh;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n  padding:0;\r\n  overflow:hidden;\r\n  background:\r\n    radial-gradient(circle at top left,rgba(70,127,247,0.14),transparent 34%),\r\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\r\n}\r\n\r\n.ols-video-title-screen,\r\n.ols-mcq-intro-screen,\r\n.ols-saq-intro{\r\n  position:absolute;\r\n  inset:0;\r\n  z-index:50;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n  background:\r\n    radial-gradient(circle at top left,rgba(70,127,247,0.14),transparent 34%),\r\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\r\n  opacity:1;\r\n  visibility:visible;\r\n  pointer-events:none;\r\n}\r\n\r\n.ols-video-title-screen.hide{animation:olsVideoTitleFadeOut 0.85s ease forwards;}\r\n.ols-mcq-intro-screen.hide{animation:olsMcqIntroFadeOut 0.85s ease forwards;}\r\n.ols-saq-intro.hide{animation:olsSaqIntroFadeOut 0.85s ease forwards;}\r\n\r\n@keyframes olsVideoTitleFadeOut{to{opacity:0;visibility:hidden;}}\r\n@keyframes olsMcqIntroFadeOut{to{opacity:0;visibility:hidden;}}\r\n@keyframes olsSaqIntroFadeOut{to{opacity:0;visibility:hidden;}}\r\n\r\n.ols-video-title-wrap,\r\n.ols-mcq-intro-title-wrap,\r\n.ols-saq-intro-title-wrap{\r\n  max-width:1250px;\r\n  padding:0 34px;\r\n  text-align:center;\r\n}\r\n\r\n.ols-video-title,\r\n.ols-mcq-intro-title,\r\n.ols-saq-intro-title{\r\n  margin:0;\r\n  font-family:Poppins,Arial,sans-serif;\r\n  font-size:clamp(52px,8vw,124px);\r\n  font-weight:600;\r\n  line-height:1.08;\r\n  color:#1C244B;\r\n  text-shadow:-9px 0 9px rgba(28,36,75,0.16);\r\n  letter-spacing:-0.045em;\r\n}\r\n\r\n#videoTitleText,\r\n#mcqIntroTitleText,\r\n#saqIntroTitleText{\r\n  white-space:pre-wrap;\r\n}\r\n\r\n.ols-video-scene{\r\n  width:100%;\r\n  height:100%;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n  opacity:0;\r\n  visibility:hidden;\r\n}\r\n\r\n.ols-video-scene.show{\r\n  visibility:visible;\r\n  animation:olsVideoSceneIn 1s ease forwards;\r\n}\r\n\r\n@keyframes olsVideoSceneIn{to{opacity:1;}}\r\n\r\n.ols-video-scale-wrap{\r\n  width:calc(var(--ols-video-screen-w) * 1px);\r\n  height:calc(var(--ols-video-screen-h) * 1px);\r\n  transform:scale(var(--ols-video-screen-scale));\r\n  transform-origin:center center;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n}\r\n\r\n.ols-video-card{\r\n  width:1180px;\r\n  height:664px;\r\n  border-radius:28px;\r\n  overflow:hidden;\r\n  background:#1C244B;\r\n  box-shadow:0 28px 80px rgba(28,36,75,0.28);\r\n  transform:translateY(24px) scale(0.96);\r\n  opacity:0;\r\n}\r\n\r\n.ols-video-scene.show .ols-video-card{\r\n  animation:olsVideoCardIn 1s cubic-bezier(.18,.89,.32,1.12) forwards;\r\n  animation-delay:0.2s;\r\n}\r\n\r\n@keyframes olsVideoCardIn{\r\n  to{\r\n    transform:translateY(0) scale(1);\r\n    opacity:1;\r\n  }\r\n}\r\n\r\n.ols-video-card video{\r\n  display:block;\r\n  width:100%;\r\n  height:100%;\r\n  aspect-ratio:16 \/ 9;\r\n  object-fit:cover;\r\n  border:0;\r\n}\r\n\r\n.ols-mcq-scale-wrap,\r\n.ols-saq-scale-wrap{\r\n  width:calc(var(--ols-mcq-screen-w) * 1px);\r\n  height:calc(var(--ols-mcq-screen-h) * 1px);\r\n  transform:scale(var(--ols-mcq-screen-scale));\r\n  transform-origin:center center;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:flex-start;\r\n}\r\n\r\n.ols-saq-scale-wrap{\r\n  width:calc(var(--ols-saq-screen-w) * 1px);\r\n  height:calc(var(--ols-saq-screen-h) * 1px);\r\n  transform:scale(var(--ols-saq-screen-scale));\r\n}\r\n\r\n.ols-mcq-screen{\r\n  width:1360px;\r\n  height:1130px;\r\n  border-radius:22px;\r\n  overflow:hidden;\r\n  background:#eaf0ff;\r\n  box-shadow:0 26px 70px rgba(28,36,75,0.22);\r\n  opacity:0;\r\n  transform:translateY(24px) scale(0.96);\r\n}\r\n\r\n.ols-mcq-screen.show{\r\n  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from{opacity:0;transform:translateY(24px) scale(0.96);}\r\n  to{opacity:1;transform:translateY(0) scale(1);}\r\n}\r\n\r\n.saq-question-area{\r\n  height:335px;\r\n  background:#eaf0ff;\r\n  padding:30px 40px 32px;\r\n}\r\n\r\n.saq-question-text{\r\n  font-size:25px;\r\n  line-height:1.42;\r\n  color:#111827;\r\n  margin-bottom:22px;\r\n}\r\n\r\n.saq-student-box{\r\n  height:195px;\r\n  background:#f3f4f6;\r\n  border:2px solid #cfd6e3;\r\n  border-radius:8px;\r\n  padding:23px 26px;\r\n  font-size:24px;\r\n  line-height:1.55;\r\n  color:#4b5563;\r\n  position:relative;\r\n  overflow:hidden;\r\n}\r\n\r\n.saq-teacher-feedback{\r\n  height:630px;\r\n  background:#dff3e6;\r\n  color:#075f3b;\r\n  padding:28px 40px 30px;\r\n  font-size:23px;\r\n  line-height:1.47;\r\n  opacity:0;\r\n  transform:translateY(20px);\r\n  transition:opacity 0.7s ease,transform 0.7s ease;\r\n  overflow:hidden;\r\n}\r\n\r\n.saq-teacher-feedback.show{\r\n  opacity:1;\r\n  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<section id=\"videoScene\" class=\"ols-video-scene\">\r\n        <div class=\"ols-video-scale-wrap\">\r\n          <div class=\"ols-video-card\">\r\n            <video\r\n              id=\"lessonVideo\"\r\n              src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Virtual-Lesson.mp4\"\r\n              muted\r\n              playsinline\r\n              preload=\"auto\">\r\n            <\/video>\r\n          <\/div>\r\n        <\/div>\r\n      <\/section>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section id=\"sceneMcq\" class=\"ols-scene\">\r\n    <div class=\"ols-mcq-stage\">\r\n      <div id=\"mcqIntroScreen\" class=\"ols-mcq-intro-screen\">\r\n        <div class=\"ols-mcq-intro-title-wrap\">\r\n          <h1 class=\"ols-mcq-intro-title\">\r\n            <span id=\"mcqIntroTitleText\"><\/span><span id=\"mcqIntroTitleCursor\" class=\"ols-title-cursor\"><\/span>\r\n          <\/h1>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <div class=\"ols-mcq-scale-wrap\">\r\n        <main id=\"mcqScreen\" class=\"ols-mcq-screen\">\r\n          <section class=\"mcq-question-area\">\r\n            <p class=\"mcq-question-lead\">Some ionic radii are shown.<\/p>\r\n\r\n            <table class=\"mcq-ionic-table\">\r\n              <thead>\r\n                <tr>\r\n                  <th>Ion<\/th>\r\n                  <th>Ionic radius \/ nm<\/th>\r\n                <\/tr>\r\n              <\/thead>\r\n              <tbody>\r\n                <tr><td>Na<sup>+<\/sup><\/td><td>0.102<\/td><\/tr>\r\n                <tr><td>K<sup>+<\/sup><\/td><td>0.138<\/td><\/tr>\r\n                <tr><td>F<sup>\u2212<\/sup><\/td><td>0.133<\/td><\/tr>\r\n                <tr><td>Cl<sup>\u2212<\/sup><\/td><td>0.180<\/td><\/tr>\r\n              <\/tbody>\r\n            <\/table>\r\n\r\n            <p class=\"mcq-question-main\">Which compound has the strongest ionic bonding?<\/p>\r\n\r\n            <div class=\"mcq-options-wrap\">\r\n              <div id=\"mcqWrongOption\" class=\"mcq-option-row\">\r\n                <span class=\"mcq-radio\"><\/span>\r\n                <span class=\"mcq-radio-ripple\"><\/span>\r\n                <span class=\"mcq-option-label\">sodium chloride<\/span>\r\n\r\n                <span id=\"mcqSpecificFeedback\" class=\"mcq-specific-feedback\">\r\n                  <span id=\"mcqCrossIcon\" class=\"mcq-cross-icon\">\u00d7<\/span>\r\n                  <span class=\"mcq-specific-feedback-text\">\r\n                    <span id=\"mcqSpecificText\"><\/span><span id=\"mcqSpecificCursor\" class=\"cursor mcq-specific-cursor\" style=\"display:none;\"><\/span>\r\n                  <\/span>\r\n                <\/span>\r\n              <\/div>\r\n\r\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">potassium chloride<\/span><\/div>\r\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">sodium fluoride<\/span><\/div>\r\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">potassium fluoride<\/span><\/div>\r\n            <\/div>\r\n\r\n            <button id=\"mcqSubmitButton\" class=\"mcq-submit-button\">Submit answer<\/button>\r\n          <\/section>\r\n\r\n          <section id=\"mcqGeneralFeedback\" class=\"mcq-general-feedback\">\r\n            <span id=\"mcqGeneralText\"><\/span><span id=\"mcqGeneralCursor\" class=\"cursor mcq-general-cursor\" style=\"display:none;\"><\/span>\r\n          <\/section>\r\n        <\/main>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section id=\"sceneSaq\" class=\"ols-scene\">\r\n    <div class=\"ols-saq-stage\">\r\n      <div id=\"saqIntro\" class=\"ols-saq-intro\">\r\n        <div class=\"ols-saq-intro-title-wrap\">\r\n          <h1 class=\"ols-saq-intro-title\">\r\n            <span id=\"saqIntroTitleText\"><\/span><span id=\"saqIntroTitleCursor\" class=\"ols-title-cursor\"><\/span>\r\n          <\/h1>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <div class=\"ols-saq-scale-wrap\">\r\n        <main id=\"saqScreen\" class=\"ols-saq-screen\">\r\n          <section class=\"saq-question-area\">\r\n            <div class=\"saq-question-text\">\r\n              <strong>(ii)<\/strong>&nbsp;&nbsp; Melting temperature depends on the strength of metallic bonding.<br>\r\n              Explain why the metallic bonding in magnesium is much stronger than that in sodium.\r\n            <\/div>\r\n\r\n            <div class=\"saq-student-box\">\r\n              <span id=\"saqStudentText\"><\/span><span id=\"saqStudentCursor\" class=\"cursor\"><\/span>\r\n            <\/div>\r\n          <\/section>\r\n\r\n          <section id=\"saqTeacherFeedback\" 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Melting temperature is a result of bonding strength, not the cause of it.\\n\\n\"+\r\n\"In metallic bonding, positive metal ions are attracted to a sea of delocalised electrons. The strength of this attraction depends on the charge of the ions and the number of delocalised electrons.\\n\\n\"+\r\n\"Magnesium forms Mg\u00b2\u207a ions and contributes two delocalised electrons per atom, whereas sodium forms Na\u207a ions and contributes only one electron. This results in a stronger electrostatic attraction in magnesium. Additionally, Mg\u00b2\u207a ions have a higher charge density than Na\u207a ions, further strengthening the metallic bonding.\\n\\n\"+\r\n\"Next time, include:\\n\"+\r\n\"\u2022 Ion charge: magnesium forms Mg\u00b2\u207a, sodium forms Na\u207a \u2713\\n\"+\r\n\"\u2022 Delocalised electrons: magnesium provides more electrons to the sea \u2713\\n\"+\r\n\"\u2022 Charge density: smaller, more highly charged ions create stronger attraction \u2713\\n\\n\"+\r\n\"You were close. 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This can make the bonding show greater covalent character.<\/p>\n          <\/div>\n\n          <div class=\"ols-faq-item\">\n            <h3>What increases the polarising power of a cation?<\/h3>\n            <p>A cation has greater polarising power when it has a higher positive charge and a smaller ionic radius. Both increase charge density.<\/p>\n          <\/div>\n\n          <div class=\"ols-faq-item\">\n            <h3>What makes an anion more polarisable?<\/h3>\n            <p>An anion is more polarisable when it is larger or has a higher negative charge. Larger anions have outer electrons further from the nucleus, so their electron clouds are easier to distort.<\/p>\n          <\/div>\n\n          <div class=\"ols-faq-item\">\n            <h3>Why does Al<sup>3+<\/sup> have strong polarising power?<\/h3>\n            <p>Al<sup>3+<\/sup> has a high positive charge and a small ionic radius, giving it a high charge density. This allows it to strongly attract and distort anion electron clouds.<\/p>\n          <\/div>\n\n          <div class=\"ols-faq-item\">\n            <h3>How does polarisation affect bonding?<\/h3>\n            <p>Greater polarisation increases covalent character because electron density is pulled towards the cation and becomes shared to a greater extent between the ions.<\/p>\n          <\/div>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-related-card\">\n        <h2>Related Revision Notes<\/h2>\n        <p>Continue building Topic 3 Chemical Bonding by linking polarisation to ionic bonding, covalent bonding and metallic bonding.<\/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\/cie\/topic-3-chemical-bonding\/ionic-bonding\/nature-of-ionic-bonding\/\">Nature of Ionic Bonding<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/ionic-bonding\/physical-properties-of-ionic-compounds\/\">Physical Properties of Ionic Compounds<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/\">Covalent Bonding<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/electronegativity\/\">Electronegativity<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/metallic-bonding\/metallic-bonding-and-structure\/\">Metallic Bonding and Structure<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/\">Topic 3 Chemical Bonding<\/a>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-attribution-card\">\n  <style>\n    .ols-attribution-card {\n      background: linear-gradient(135deg, #ffffff, #f8fbff);\n      border: 1px solid rgba(28, 36, 75, 0.14);\n      border-radius: 28px;\n      box-shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      padding: 34px;\n      margin-bottom: 24px;\n      overflow: hidden;\n      font-family: Poppins, Arial, sans-serif;\n      box-sizing: border-box;\n    }\n\n    .ols-attribution-card,\n    .ols-attribution-card * {\n      box-sizing: border-box;\n    }\n\n    .ols-attribution-card p {\n      margin: 0;\n      font-size: 14px;\n      line-height: 1.65;\n      font-weight: 300;\n      color: #667085;\n    }\n\n    .ols-attribution-card strong {\n      font-weight: 700;\n      color: #1C244B;\n    }\n\n    @media (max-width: 760px) {\n      .ols-attribution-card {\n        padding: 24px 18px;\n        border-radius: 22px;\n      }\n    }\n  <\/style>\n\n  <p><strong>Copyright notice:<\/strong> This OLS revision content, including the explanations, layout, diagrams, tables and embedded learning structure, is authored for Online Learning System by Dr. Mohammed Al-Fatah. 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