{"id":4839,"date":"2026-06-03T06:24:39","date_gmt":"2026-06-03T05:24:39","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/geometric-isomerism\/"},"modified":"2026-06-03T11:23:29","modified_gmt":"2026-06-03T10:23:29","slug":"geometric-isomerism","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/geometric-isomerism\/","title":{"rendered":"Geometric Isomerism"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-geometric-isomerism-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      --gold: #c9973a;\n      --grey-text: #667085;\n      --body-text: #1f2937;\n      --border: rgba(28, 36, 75, 0.14);\n     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  <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 6 Organic Chemistry I<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/\">Introduction to Organic Chemistry<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/iupac-rules\/\">IUPAC Rules<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/alkene\/\">Alkene<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/alcohol\/\">Alcohol<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/halogenoalkanes\/\">Halogenoalkanes<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/aldehyde\/\">Aldehyde<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/ketone\/\">Ketone<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/carboxylic-acid\/\">Carboxylic Acid<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/ester\/\">Ester<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/isomerism\/\">Isomerism<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/\">Alkanes<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/\">Alkanes from Crude Oil<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/fractional-distillation\/\">Fractional Distillation<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/cracking\/\">Cracking<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/reforming\/\">Reforming<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/\">Alkanes as Fuel<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/combustion\/\">Combustion<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/oxides-of-sulfur\/\">Oxides of Sulfur<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/oxides-of-nitrogen\/\">Oxides of Nitrogen<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/catalytic-converter\/\">Catalytic Converter<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/alternative-fuel\/\">Alternative Fuel<\/a>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/\">Reactions of Alkanes<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/free-radical-substitution\/\">Free Radical Substitution<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/initiation\/\">Initiation<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/propagation\/\">Propagation<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/termination\/\">Termination<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/further-substitution\/\">Further Substitution<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/\">Alkenes<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/alkene-bonding\/\">Alkene Bonding<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/geometric-isomerism\/\">Geometric Isomerism<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/electrophilic-addition-mechanism\/\">Electrophilic Addition Mechanism<\/a>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/\">Reactions of Alkenes<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/halogens\/\">Halogens<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/hydrogen-halide\/\">Hydrogen Halide<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/bromine-water\/\">Bromine Water<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/hydrogen\/\">Hydrogen<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/steam\/\">Steam<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/kmno4\/\">KMnO4<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/polymerisation-reactions\/\">Polymerisation Reactions<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/polymer-waste\/\">Polymer Waste<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/halogenoalkanes\/\">Halogenoalkanes<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alcohols\/\">Alcohols<\/a>\r\n      <\/li>\r\n\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Next Topics<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-7-modern-analytical-techniques-i\/\">Topic 7 Modern Analytical Techniques I<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-5-formulae-equations-and-amounts-of-substance\/\">Topic 5 Formulae, Equations &amp; Amounts<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/\">Topic 4 Inorganic Chemistry &amp; The Periodic Table<\/a>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n<\/aside>\r\n\r\n<script>\r\n(function() {\r\n  function normalisePath(path) {\r\n    return String(path || '')\r\n      .split('?')[0]\r\n      .split('#')[0]\r\n      .replace(\/\\\/+$\/, '')\r\n      .toLowerCase();\r\n  }\r\n\r\n  function highlightActive() {\r\n    var sidebar = document.querySelector('.ols-sidebar');\r\n    if (!sidebar) return false;\r\n\r\n    var currentPath = normalisePath(window.location.pathname);\r\n    var links = sidebar.querySelectorAll('a[href]');\r\n    var matched = null;\r\n    var matchedLength = 0;\r\n\r\n    sidebar.querySelectorAll('.active, .active-main, .parent-active').forEach(function(item) {\r\n      item.classList.remove('active', 'active-main', 'parent-active');\r\n    });\r\n\r\n    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'-1');\r\n          matched.setAttribute('data-ols-disabled-parent', '1');\r\n        }\r\n      }\r\n    }\r\n\r\n    return true;\r\n  }\r\n\r\n  if (!highlightActive()) {\r\n    document.addEventListener('DOMContentLoaded', highlightActive);\r\n  }\r\n})();\r\n<\/script>\n\n  <main class=\"ols-main\">\n      <nav class=\"ols-breadcrumbs\" aria-label=\"Breadcrumb\">\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\">Revision Notes<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\">A Level Chemistry<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/\">Edexcel<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/\">Topic 6 Organic Chemistry I<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/\">Alkenes<\/a> \/\n        <span>Geometric Isomerism<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Geometric Isomerism<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to stereoisomerism in alkenes, restricted rotation around C=C bonds, E-Z naming, priority groups and the link between E-Z and cis-trans isomerism.<\/p>\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Paper 2<\/div>\n          <div class=\"ols-badge\">Topic 6: Organic Chemistry I<\/div>\n          <div class=\"ols-badge\">9CH0\/02<\/div>\n        <\/div>\n        <div class=\"ols-author\">\n\n    <img decoding=\"async\"\n      class=\"ols-author-avatar-img\"\n      src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\"\n      alt=\"Dr. Mohammed Al-Fatah\"\n    >\n\n    <div class=\"ols-author-content\">\n\n      <h2 class=\"ols-author-title\">\n        Written by: Dr. Mohammed Al-Fatah\n      <\/h2>\n\n      <p class=\"ols-author-description\">\n        Chemistry specialist revision notes for A Level Chemistry.\n      <\/p>\n\n      <a class=\"ols-linkedin-pill\" href=\"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\" target=\"_blank\" rel=\"noopener noreferrer\">\n        <svg class=\"ols-linkedin-icon\" viewBox=\"0 0 24 24\" fill=\"currentColor\" aria-hidden=\"true\">\n          <path d=\"M4.98 3.5C4.98 4.88 3.86 6 2.48 6S0 4.88 0 3.5 1.12 1 2.48 1s2.5 1.12 2.5 2.5zM.5 8h4V24h-4V8zm7 0h3.8v2.2h.1c.5-.9 1.8-2.2 3.9-2.2 4.2 0 5 2.8 5 6.4V24h-4v-7.6c0-1.8 0-4.2-2.6-4.2s-3 2-3 4v7.8h-4V8z\"\/>\n        <\/svg>\n        View LinkedIn Profile\n      <\/a>\n\n    <\/div>\n\n  <\/div>\n      <\/header>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">1<\/div><h2>What Are Stereoisomers?<\/h2><\/div>\n        <p><strong>Stereoisomers<\/strong> are compounds with the same structural formula but a different three-dimensional arrangement of atoms in space.<\/p>\n        <p>In alkenes, this matters because the <strong>C=C double bond restricts rotation<\/strong>. The atoms or groups attached to the double bond cannot freely rotate into a new arrangement without breaking the pi bond.<\/p>\n        <p>This produces a type of stereoisomerism called <strong>E-Z stereoisomerism<\/strong>, also called geometric isomerism.<\/p>\n        <div class=\"ols-key-box\"><p><strong>Key idea:<\/strong> E-Z isomers are not structural isomers. They have the same connectivity, but different spatial arrangement around the carbon-carbon double bond.<\/p><\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">2<\/div><h2>Why E-Z Isomerism Occurs<\/h2><\/div>\n        <p>E-Z isomerism occurs because the carbon-carbon double bond contains a <strong>pi bond<\/strong>. Rotation around the C=C bond is restricted because rotating one carbon would break the sideways overlap of the p orbitals.<\/p>\n        <p>By contrast, a carbon-carbon single bond can rotate freely. This is why simple alkanes do not usually produce this type of fixed geometric arrangement.<\/p>\n        <div class=\"ols-key-box\"><p><strong>Exam focus:<\/strong> Always link E-Z isomerism to <strong>restricted rotation around the C=C double bond<\/strong>.<\/p><\/div>\n        <div class=\"ols-figure-card ols-zoom-pop\">\n          <div class=\"ols-figure-image\">\n            <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/T5.2-e-but-2-ene.webp\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/T5.2-e-but-2-ene.webp\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/T5.2-e-but-2-ene.webp\" alt=\"Chemical structure of E-but-2-ene.\"><\/a>\n          <\/div>\n        <\/div>\n        <div class=\"ols-figure-card ols-zoom-pop\">\n          <div class=\"ols-figure-image\">\n            <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/T5.2-e-but-2-ene-2.webp\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/T5.2-e-but-2-ene-2.webp\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/T5.2-e-but-2-ene-2.webp\" alt=\"Chemical structure and stereochemistry explanation\"><\/a>\n          <\/div>\n        <\/div>\n      <\/article>\n\n<div class=\"ols-sigma-rot-card-001\">\n  <style>\n    @import url('https:\/\/fonts.googleapis.com\/css2?family=Poppins:wght@300;400;500;600;700&display=swap');\n\n    .ols-sigma-rot-card-001,\n    .ols-sigma-rot-card-001 * {\n      box-sizing: border-box;\n    }\n\n    .ols-sigma-rot-card-001 {\n      --ols-navy: #1C244B;\n      --ols-blue: 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.ols-sigma-rot-card-001 .ols-sigma-overlay {\n        top: 12px;\n        right: 12px;\n        font-size: 12px;\n      }\n\n      .ols-sigma-rot-card-001 .ols-sigma-label {\n        left: 12px;\n        right: 12px;\n        bottom: 12px;\n        max-width: none;\n      }\n\n      .ols-sigma-rot-card-001 .ols-sigma-status {\n        left: 12px;\n        top: 12px;\n      }\n    }\n  <\/style>\n\n  <div class=\"ols-sigma-card\">\n    <div class=\"ols-sigma-header\">\n      <div>\n        <div class=\"ols-sigma-kicker\">3D model \u00b7 Free rotation around a \u03c3 bond<\/div>\n        <h2 class=\"ols-sigma-title\">Chloroethane: rotation around the C-C single bond<\/h2>\n        <p class=\"ols-sigma-subtitle\">\n          The C-C single bond is a \u03c3 bond. In this model, the CH\u2083 side remains fixed while the CH\u2082Cl side rotates slowly around the C-C bond axis.\n        <\/p>\n      <\/div>\n\n      <div class=\"ols-sigma-controls\">\n        <button id=\"olsSigmaRotateBtn001\" class=\"ols-sigma-btn ols-sigma-btn-main\" type=\"button\">\n          Rotate sigma bond\n        <\/button>\n        <button id=\"olsSigmaResetBtn001\" class=\"ols-sigma-btn ols-sigma-btn-secondary\" type=\"button\">\n          Reset view\n        <\/button>\n      <\/div>\n    <\/div>\n\n    <div class=\"ols-sigma-view-wrap\">\n      <canvas id=\"olsSigmaCanvas001\" aria-label=\"3D model showing free rotation around the carbon carbon sigma bond in chloroethane\"><\/canvas>\n\n      <div class=\"ols-sigma-status\">\n        <span class=\"ols-sigma-dot\"><\/span>\n        C-C \u03c3 bond centred\n      <\/div>\n\n      <div class=\"ols-sigma-overlay\">\n        Drag to rotate view \u00b7 Scroll to zoom\n      <\/div>\n\n      <div class=\"ols-sigma-label\">\n        <strong>Model focus:<\/strong> the highlighted central C-C \u03c3 bond allows rotation because electron density lies directly along the internuclear axis.\n      <\/div>\n    <\/div>\n  <\/div>\n\n  <script>\n    (function(){\n      var scriptUrl = \"https:\/\/cdn.jsdelivr.net\/npm\/three@0.160.0\/build\/three.min.js\";\n      var canvasId = \"olsSigmaCanvas001\";\n      var rotateBtnId = \"olsSigmaRotateBtn001\";\n      var resetBtnId = \"olsSigmaResetBtn001\";\n\n      function loadThreeThenStart(callback){\n        if (window.THREE) {\n          callback();\n          return;\n        }\n\n        if (window.olsThreeLoading001) {\n          window.olsThreeCallbacks001.push(callback);\n          return;\n        }\n\n        window.olsThreeLoading001 = true;\n        window.olsThreeCallbacks001 = [callback];\n\n        var script = document.createElement(\"script\");\n        script.src = scriptUrl;\n        script.onload = function(){\n          var list = window.olsThreeCallbacks001;\n          for (var i = 0; i < list.length; i++) {\n            list[i]();\n          }\n        };\n        document.head.appendChild(script);\n      }\n\n      function startSigmaModel(){\n        var canvas = document.getElementById(canvasId);\n        var rotateBtn = document.getElementById(rotateBtnId);\n        var resetBtn = document.getElementById(resetBtnId);\n\n        if (!canvas) {\n          return;\n        }\n\n        if (!window.THREE) {\n          return;\n        }\n\n        var THREE = window.THREE;\n\n        var renderer = new THREE.WebGLRenderer({\n          canvas: canvas,\n          antialias: true,\n          alpha: true\n        });\n\n        renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2));\n        renderer.setClearColor(0xffffff, 0);\n\n        var scene = new THREE.Scene();\n\n        var camera = new THREE.PerspectiveCamera(38, 1, 0.1, 100);\n        camera.position.set(0, 2.4, 7.2);\n\n        var root = new THREE.Group();\n        root.scale.set(0.78, 0.78, 0.78);\n        scene.add(root);\n\n        var molecule = new THREE.Group();\n        molecule.rotation.y = -0.35;\n        molecule.rotation.x = 0.22;\n        root.add(molecule);\n\n        var fixedSide = new THREE.Group();\n        var rotatingSide = new THREE.Group();\n        molecule.add(fixedSide);\n        molecule.add(rotatingSide);\n\n        var ambient = new THREE.AmbientLight(0xffffff, 0.82);\n        scene.add(ambient);\n\n        var keyLight = new THREE.DirectionalLight(0xffffff, 1.35);\n        keyLight.position.set(4, 5, 6);\n        scene.add(keyLight);\n\n        var fillLight = new THREE.DirectionalLight(0xffffff, 0.65);\n        fillLight.position.set(-4, -2, 3);\n        scene.add(fillLight);\n\n        var colours = {\n          carbon: 0x2f3542,\n          hydrogen: 0xf2f4f7,\n          chlorine: 0x37b24d,\n          bond: 0xa3aab8,\n          sigma: 0x467ff7\n        };\n\n        var radii = {\n          carbon: 0.24,\n          hydrogen: 0.15,\n          chlorine: 0.31\n        };\n\n        var c1 = new THREE.Vector3(-0.72, 0, 0);\n        var c2 = new THREE.Vector3(0.72, 0, 0);\n\n        var chLength = 1.08;\n        var cclLength = 1.78;\n\n        function atomMaterial(hex, roughnessValue, metalnessValue){\n          return new THREE.MeshStandardMaterial({\n            color: hex,\n            roughness: roughnessValue,\n            metalness: metalnessValue\n          });\n        }\n\n        var matCarbon = atomMaterial(colours.carbon, 0.38, 0.04);\n        var matHydrogen = atomMaterial(colours.hydrogen, 0.28, 0.02);\n        var matChlorine = atomMaterial(colours.chlorine, 0.34, 0.03);\n        var matBond = atomMaterial(colours.bond, 0.42, 0.02);\n        var matSigma = atomMaterial(colours.sigma, 0.28, 0.05);\n\n        var sphereGeoCarbon = new THREE.SphereGeometry(radii.carbon, 40, 40);\n        var sphereGeoHydrogen = new THREE.SphereGeometry(radii.hydrogen, 32, 32);\n        var sphereGeoChlorine = new THREE.SphereGeometry(radii.chlorine, 40, 40);\n\n        function addAtom(parent, position, geometry, material, labelText){\n          var atom = new THREE.Mesh(geometry, material);\n          atom.position.copy(position);\n          parent.add(atom);\n\n          var label = makeTextSprite(labelText);\n          label.position.copy(position.clone().add(new THREE.Vector3(0, 0.42, 0)));\n          parent.add(label);\n\n          return atom;\n        }\n\n        function makeTextSprite(text){\n          var labelCanvas = document.createElement(\"canvas\");\n          labelCanvas.width = 256;\n          labelCanvas.height = 128;\n\n          var ctx = labelCanvas.getContext(\"2d\");\n          ctx.clearRect(0, 0, labelCanvas.width, labelCanvas.height);\n          ctx.font = \"600 42px Poppins, Arial\";\n          ctx.textAlign = \"center\";\n          ctx.textBaseline = \"middle\";\n          ctx.fillStyle = \"#1C244B\";\n          ctx.fillText(text, 128, 64);\n\n          var texture = new THREE.CanvasTexture(labelCanvas);\n          var material = new THREE.SpriteMaterial({\n            map: texture,\n            transparent: true,\n            depthWrite: false\n          });\n\n          var sprite = new THREE.Sprite(material);\n          sprite.scale.set(0.46, 0.23, 1);\n          return sprite;\n        }\n\n        function cylinderBetween(parent, start, end, radius, material){\n          var direction = new THREE.Vector3().subVectors(end, start);\n          var length = direction.length();\n\n          var geometry = new THREE.CylinderGeometry(radius, radius, length, 24, 1, false);\n          var cylinder = new THREE.Mesh(geometry, material);\n\n          var midpoint = new THREE.Vector3().addVectors(start, end).multiplyScalar(0.5);\n          cylinder.position.copy(midpoint);\n\n          var yAxis = new THREE.Vector3(0, 1, 0);\n          direction.normalize();\n          var quaternion = new THREE.Quaternion();\n          quaternion.setFromUnitVectors(yAxis, direction);\n          cylinder.quaternion.copy(quaternion);\n\n          parent.add(cylinder);\n          return cylinder;\n        }\n\n        function localSubstituent(length, angleDegrees){\n          var x = length \/ 3;\n          var radiusYZ = Math.sqrt(8 \/ 9) * length;\n          var angle = angleDegrees * Math.PI \/ 180;\n          var y = radiusYZ * Math.cos(angle);\n          var z = radiusYZ * Math.sin(angle);\n          return new THREE.Vector3(x, y, z);\n        }\n\n        function fixedSubstituent(length, angleDegrees){\n          var x = -length \/ 3;\n          var radiusYZ = Math.sqrt(8 \/ 9) * length;\n          var angle = angleDegrees * Math.PI \/ 180;\n          var y = radiusYZ * Math.cos(angle);\n          var z = radiusYZ * Math.sin(angle);\n          return new THREE.Vector3(x, y, z);\n        }\n\n        addAtom(fixedSide, c1, sphereGeoCarbon, matCarbon, \"C\");\n        addAtom(rotatingSide, new THREE.Vector3(0, 0, 0), sphereGeoCarbon, matCarbon, \"C\");\n        rotatingSide.position.copy(c2);\n\n        cylinderBetween(molecule, c1, c2, 0.08, matSigma);\n\n        var h1 = c1.clone().add(fixedSubstituent(chLength, 90));\n        var h2 = c1.clone().add(fixedSubstituent(chLength, 210));\n        var h3 = c1.clone().add(fixedSubstituent(chLength, 330));\n\n        addAtom(fixedSide, h1, sphereGeoHydrogen, matHydrogen, \"H\");\n        addAtom(fixedSide, h2, sphereGeoHydrogen, matHydrogen, \"H\");\n        addAtom(fixedSide, h3, sphereGeoHydrogen, matHydrogen, \"H\");\n\n        cylinderBetween(fixedSide, c1, h1, 0.045, matBond);\n        cylinderBetween(fixedSide, c1, h2, 0.045, matBond);\n        cylinderBetween(fixedSide, c1, h3, 0.045, matBond);\n\n        var localH4 = localSubstituent(chLength, 85);\n        var localH5 = localSubstituent(chLength, 225);\n        var localCl = localSubstituent(cclLength, 335);\n\n        addAtom(rotatingSide, localH4, sphereGeoHydrogen, matHydrogen, \"H\");\n        addAtom(rotatingSide, localH5, sphereGeoHydrogen, matHydrogen, \"H\");\n        addAtom(rotatingSide, localCl, sphereGeoChlorine, matChlorine, \"Cl\");\n\n        cylinderBetween(rotatingSide, new THREE.Vector3(0, 0, 0), localH4, 0.045, matBond);\n        cylinderBetween(rotatingSide, new THREE.Vector3(0, 0, 0), localH5, 0.045, matBond);\n        cylinderBetween(rotatingSide, new THREE.Vector3(0, 0, 0), localCl, 0.055, matBond);\n\n        var axisGeo = new THREE.CylinderGeometry(0.025, 0.025, 2.35, 32, 1, false);\n        var axisMat = new THREE.MeshStandardMaterial({\n          color: colours.sigma,\n          roughness: 0.25,\n          metalness: 0.1,\n          transparent: true,\n          opacity: 0.45\n        });\n        var axis = new THREE.Mesh(axisGeo, axisMat);\n        axis.rotation.z = Math.PI \/ 2;\n        axis.position.set(0, 0, 0);\n        molecule.add(axis);\n\n        var arrowGroup = new THREE.Group();\n        molecule.add(arrowGroup);\n\n        var torusGeo = new THREE.TorusGeometry(1.15, 0.018, 12, 96, Math.PI * 1.55);\n        var torusMat = new THREE.MeshStandardMaterial({\n          color: colours.sigma,\n          roughness: 0.22,\n          metalness: 0.04,\n          transparent: true,\n          opacity: 0.82\n        });\n        var torus = new THREE.Mesh(torusGeo, torusMat);\n        torus.rotation.y = Math.PI \/ 2;\n        torus.position.set(0, 0, 0);\n        arrowGroup.add(torus);\n\n        var coneGeo = new THREE.ConeGeometry(0.09, 0.22, 32);\n        var cone = new THREE.Mesh(coneGeo, torusMat);\n        cone.position.set(0, -0.95, 0.62);\n        cone.rotation.z = -0.7;\n        cone.rotation.x = Math.PI \/ 2;\n        arrowGroup.add(cone);\n\n        var labelSigma = makeTextSprite(\"\u03c3 bond\");\n        labelSigma.position.set(0, -0.55, 0);\n        labelSigma.scale.set(0.72, 0.36, 1);\n        molecule.add(labelSigma);\n\n        var isSigmaRotating = false;\n        var sceneRotX = 0.22;\n        var sceneRotY = -0.35;\n        var targetRotX = sceneRotX;\n        var targetRotY = sceneRotY;\n        var zoomDistance = 7.2;\n\n        var dragging = false;\n        var lastX = 0;\n        var lastY = 0;\n\n        canvas.addEventListener(\"mousedown\", function(event){\n          dragging = true;\n          lastX = event.clientX;\n          lastY = event.clientY;\n        });\n\n        window.addEventListener(\"mouseup\", function(){\n          dragging = false;\n        });\n\n        window.addEventListener(\"mousemove\", function(event){\n          if (dragging) {\n            var dx = event.clientX - lastX;\n            var dy = event.clientY - lastY;\n            targetRotY = targetRotY + dx * 0.006;\n            targetRotX = targetRotX + dy * 0.006;\n            lastX = event.clientX;\n            lastY = event.clientY;\n          }\n        });\n\n        canvas.addEventListener(\"touchstart\", function(event){\n          if (event.touches.length === 1) {\n            dragging = true;\n            lastX = event.touches[0].clientX;\n            lastY = event.touches[0].clientY;\n          }\n        }, { passive: true });\n\n        canvas.addEventListener(\"touchend\", function(){\n          dragging = false;\n        }, { passive: true });\n\n        canvas.addEventListener(\"touchmove\", function(event){\n          if (dragging) {\n            if (event.touches.length === 1) {\n              var dx = event.touches[0].clientX - lastX;\n              var dy = event.touches[0].clientY - lastY;\n              targetRotY = targetRotY + dx * 0.006;\n              targetRotX = targetRotX + dy * 0.006;\n              lastX = event.touches[0].clientX;\n              lastY = event.touches[0].clientY;\n            }\n          }\n        }, { passive: true });\n\n        canvas.addEventListener(\"wheel\", function(event){\n          event.preventDefault();\n          zoomDistance = zoomDistance + event.deltaY * 0.005;\n\n          if (zoomDistance < 4.4) {\n            zoomDistance = 4.4;\n          }\n\n          if (zoomDistance > 10.5) {\n            zoomDistance = 10.5;\n          }\n        }, { passive: false });\n\n        if (rotateBtn) {\n          rotateBtn.addEventListener(\"click\", function(){\n            isSigmaRotating = !isSigmaRotating;\n\n            if (isSigmaRotating) {\n              rotateBtn.classList.add(\"is-active\");\n              rotateBtn.textContent = \"Pause sigma rotation\";\n            } else {\n              rotateBtn.classList.remove(\"is-active\");\n              rotateBtn.textContent = \"Rotate sigma bond\";\n            }\n          });\n        }\n\n        if (resetBtn) {\n          resetBtn.addEventListener(\"click\", function(){\n            targetRotX = 0.22;\n            targetRotY = -0.35;\n            zoomDistance = 7.2;\n            rotatingSide.rotation.x = 0;\n          });\n        }\n\n        function resizeRenderer(){\n          var rect = canvas.getBoundingClientRect();\n          var width = Math.max(1, Math.floor(rect.width));\n          var height = Math.max(1, Math.floor(rect.height));\n\n          if (canvas.width !== width * renderer.getPixelRatio()) {\n            renderer.setSize(width, height, false);\n            camera.aspect = width \/ height;\n            camera.updateProjectionMatrix();\n          }\n        }\n\n        var isCanvasVisible = false;\n        var animationFrameId = null;\n\n        function startAnimationLoop(){\n          if (animationFrameId === null) {\n            animationFrameId = requestAnimationFrame(animate);\n          }\n        }\n\n        function stopAnimationLoop(){\n          if (animationFrameId !== null) {\n            cancelAnimationFrame(animationFrameId);\n            animationFrameId = null;\n          }\n        }\n\n        function animate(){\n          if (!isCanvasVisible) {\n            animationFrameId = null;\n            return;\n          }\n\n          animationFrameId = requestAnimationFrame(animate);\n          resizeRenderer();\n\n          sceneRotX = sceneRotX + (targetRotX - sceneRotX) * 0.08;\n          sceneRotY = sceneRotY + (targetRotY - sceneRotY) * 0.08;\n\n          molecule.rotation.x = sceneRotX;\n          molecule.rotation.y = sceneRotY;\n\n          camera.position.z = zoomDistance;\n          camera.lookAt(0, 0, 0);\n\n          if (isSigmaRotating) {\n            rotatingSide.rotation.x = rotatingSide.rotation.x + 0.008;\n            arrowGroup.rotation.x = arrowGroup.rotation.x + 0.008;\n          }\n\n          renderer.render(scene, camera);\n        }\n\n        function setCanvasVisibility(isVisible){\n          isCanvasVisible = isVisible;\n\n          if (isCanvasVisible) {\n            startAnimationLoop();\n          } else {\n            stopAnimationLoop();\n          }\n        }\n\n        if (\"IntersectionObserver\" in window) {\n          var sigmaObserver = new IntersectionObserver(function(entries){\n            setCanvasVisibility(entries[0].isIntersecting);\n          }, {\n            threshold: 0.05\n          });\n\n          sigmaObserver.observe(canvas);\n        } else {\n          setCanvasVisibility(true);\n        }\n      }\n\n      document.addEventListener(\"DOMContentLoaded\", function(){\n        loadThreeThenStart(startSigmaModel);\n      });\n    })();\n  <\/script>\n<\/div>\n\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">3<\/div><h2>Conditions for E-Z Stereoisomerism<\/h2><\/div>\n        <p>For an alkene to show E-Z stereoisomerism, <strong>two conditions<\/strong> must both be met:<\/p>\n        <ol>\n          <li>There must be <strong>restricted rotation<\/strong> about the carbon-carbon double bond.<\/li>\n          <li>Each carbon atom of the C=C bond must be attached to <strong>two different atoms or groups<\/strong>.<\/li>\n        <\/ol>\n        <p>If either carbon in the C=C bond has two identical groups attached, E-Z isomerism is not possible.<\/p>\n        <div class=\"ols-figure-card ols-zoom-pop\">\n          <div class=\"ols-figure-image\">\n            <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/T5.2-but-2-ene.webp\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/T5.2-but-2-ene.webp\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/T5.2-but-2-ene.webp\" alt=\"But-1-ene structure and isomerism explanation\"><\/a>\n          <\/div>\n        <\/div>\n      <\/article>\n\n<div class=\"ols-pi-rot-card-002\">\n  <style>\n    @import url('https:\/\/fonts.googleapis.com\/css2?family=Poppins:wght@300;400;500;600;700&display=swap');\n\n    .ols-pi-rot-card-002,\n    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.ols-pi-view-wrap {\n        height: 420px;\n      }\n\n      .ols-pi-rot-card-002 .ols-pi-overlay {\n        top: 12px;\n        right: 12px;\n        font-size: 12px;\n      }\n\n      .ols-pi-rot-card-002 .ols-pi-label {\n        left: 12px;\n        right: 12px;\n        bottom: 12px;\n        max-width: none;\n      }\n\n      .ols-pi-rot-card-002 .ols-pi-alert {\n        top: 16px;\n        font-size: 13px;\n        max-width: calc(100% - 24px);\n        text-align: center;\n        white-space: normal;\n      }\n    }\n  <\/style>\n\n  <div class=\"ols-pi-card\">\n    <div class=\"ols-pi-header\">\n      <div>\n        <div class=\"ols-pi-kicker\">3D model \u00b7 Restricted rotation around a \u03c0 bond<\/div>\n        <h2 class=\"ols-pi-title\">1,2-Dichloroethene: restricted rotation around the C=C bond<\/h2>\n        <p class=\"ols-pi-subtitle\">\n          The C=C double bond contains a \u03c0 bond. When one side tries to rotate, the sideways overlap needed for the \u03c0 bond would be disrupted, so the molecule is knocked back instead of rotating freely.\n        <\/p>\n      <\/div>\n\n      <div class=\"ols-pi-controls\">\n        <button id=\"olsPiRotateBtn002\" class=\"ols-pi-btn ols-pi-btn-main\" type=\"button\">\n          Rotate pi bond\n        <\/button>\n        <button id=\"olsPiResetBtn002\" class=\"ols-pi-btn ols-pi-btn-secondary\" type=\"button\">\n          Reset view\n        <\/button>\n      <\/div>\n    <\/div>\n\n    <div class=\"ols-pi-view-wrap\">\n      <canvas id=\"olsPiCanvas002\" aria-label=\"3D model showing restricted rotation around the carbon carbon double bond in 1,2-dichloroethene\"><\/canvas>\n\n      <div class=\"ols-pi-overlay\">\n        Drag to rotate view \u00b7 Scroll to zoom\n      <\/div>\n\n      <div class=\"ols-pi-label\">\n        <strong>Model focus:<\/strong> the double bond prevents free rotation because twisting would break the sideways overlap that forms the \u03c0 bond.\n      <\/div>\n\n      <div id=\"olsPiAlert002\" class=\"ols-pi-alert\">Restricted rotation<\/div>\n    <\/div>\n  <\/div>\n\n  <script>\n    (function(){\n      var scriptUrl = \"https:\/\/cdn.jsdelivr.net\/npm\/three@0.160.0\/build\/three.min.js\";\n      var canvasId = \"olsPiCanvas002\";\n      var rotateBtnId = \"olsPiRotateBtn002\";\n      var resetBtnId = \"olsPiResetBtn002\";\n      var alertId = \"olsPiAlert002\";\n\n      function loadThreeShared(callback){\n        if (window.THREE) {\n          callback();\n          return;\n        }\n\n        if (!window.olsThreeSharedCallbacks) {\n          window.olsThreeSharedCallbacks = [];\n        }\n\n        window.olsThreeSharedCallbacks.push(callback);\n\n        if (window.olsThreeSharedLoading) {\n          return;\n        }\n\n        window.olsThreeSharedLoading = true;\n\n        var script = document.createElement(\"script\");\n        script.src = scriptUrl;\n        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doubleBond: 0x467ff7,\n          alert: 0xc81e1e\n        };\n\n        var radii = {\n          carbon: 0.24,\n          hydrogen: 0.15,\n          chlorine: 0.31\n        };\n\n        var c1 = new THREE.Vector3(-0.72, 0, 0);\n        var c2 = new THREE.Vector3(0.72, 0, 0);\n\n        function atomMaterial(hex, roughnessValue, metalnessValue){\n          return new THREE.MeshStandardMaterial({\n            color: hex,\n            roughness: roughnessValue,\n            metalness: metalnessValue\n          });\n        }\n\n        var matCarbon = atomMaterial(colours.carbon, 0.38, 0.04);\n        var matHydrogen = atomMaterial(colours.hydrogen, 0.28, 0.02);\n        var matChlorine = atomMaterial(colours.chlorine, 0.34, 0.03);\n        var matSingleBond = atomMaterial(colours.singleBond, 0.42, 0.02);\n\n        var matDoubleBondA = new THREE.MeshStandardMaterial({\n          color: colours.doubleBond,\n          roughness: 0.28,\n          metalness: 0.05,\n          emissive: 0xc81e1e,\n          emissiveIntensity: 0\n        });\n\n        var matDoubleBondB = new THREE.MeshStandardMaterial({\n          color: colours.doubleBond,\n          roughness: 0.28,\n          metalness: 0.05,\n          emissive: 0xc81e1e,\n          emissiveIntensity: 0\n        });\n\n        var sphereGeoCarbon = new THREE.SphereGeometry(radii.carbon, 40, 40);\n        var sphereGeoHydrogen = new THREE.SphereGeometry(radii.hydrogen, 32, 32);\n        var sphereGeoChlorine = new THREE.SphereGeometry(radii.chlorine, 40, 40);\n\n        function makeTextSprite(text){\n          var labelCanvas = document.createElement(\"canvas\");\n          labelCanvas.width = 256;\n          labelCanvas.height = 128;\n\n          var ctx = labelCanvas.getContext(\"2d\");\n          ctx.clearRect(0, 0, labelCanvas.width, labelCanvas.height);\n          ctx.font = \"600 42px Poppins, Arial\";\n          ctx.textAlign = \"center\";\n          ctx.textBaseline = \"middle\";\n          ctx.fillStyle = \"#1C244B\";\n          ctx.fillText(text, 128, 64);\n\n          var texture = new THREE.CanvasTexture(labelCanvas);\n          var material = new THREE.SpriteMaterial({\n            map: texture,\n            transparent: true,\n            depthWrite: false\n          });\n\n          var sprite = new THREE.Sprite(material);\n          sprite.scale.set(0.46, 0.23, 1);\n          return sprite;\n        }\n\n        function addAtom(parent, position, geometry, material, labelText){\n          var atom = new THREE.Mesh(geometry, material);\n          atom.position.copy(position);\n          parent.add(atom);\n\n          var label = makeTextSprite(labelText);\n          label.position.copy(position.clone().add(new THREE.Vector3(0, 0.42, 0)));\n          parent.add(label);\n\n          return atom;\n        }\n\n        function cylinderBetween(parent, start, end, radius, material){\n          var direction = new THREE.Vector3().subVectors(end, start);\n          var length = direction.length();\n\n          var geometry = new THREE.CylinderGeometry(radius, radius, length, 24, 1, false);\n          var cylinder = new THREE.Mesh(geometry, material);\n\n          var midpoint = new THREE.Vector3().addVectors(start, end).multiplyScalar(0.5);\n          cylinder.position.copy(midpoint);\n\n          var yAxis = new THREE.Vector3(0, 1, 0);\n          direction.normalize();\n          var quaternion = new THREE.Quaternion();\n          quaternion.setFromUnitVectors(yAxis, direction);\n          cylinder.quaternion.copy(quaternion);\n\n          parent.add(cylinder);\n          return cylinder;\n        }\n\n        var fixedSide = new THREE.Group();\n        molecule.add(fixedSide);\n\n        var rotatingSide = new THREE.Group();\n        rotatingSide.position.copy(c2);\n        molecule.add(rotatingSide);\n\n        addAtom(fixedSide, c1, sphereGeoCarbon, matCarbon, \"C\");\n        addAtom(rotatingSide, new THREE.Vector3(0, 0, 0), sphereGeoCarbon, matCarbon, \"C\");\n\n        var bondOffset = 0.085;\n        var dblStart1 = c1.clone().add(new THREE.Vector3(0, 0, bondOffset));\n        var dblEnd1 = c2.clone().add(new THREE.Vector3(0, 0, bondOffset));\n        var dblStart2 = c1.clone().add(new THREE.Vector3(0, 0, -bondOffset));\n        var dblEnd2 = c2.clone().add(new THREE.Vector3(0, 0, -bondOffset));\n\n        cylinderBetween(molecule, dblStart1, dblEnd1, 0.052, matDoubleBondA);\n        cylinderBetween(molecule, dblStart2, dblEnd2, 0.052, matDoubleBondB);\n\n        var leftCl = c1.clone().add(new THREE.Vector3(-0.88, 0.96, 0));\n        var leftH = c1.clone().add(new THREE.Vector3(-0.96, -0.90, 0));\n\n        addAtom(fixedSide, leftCl, sphereGeoChlorine, matChlorine, \"Cl\");\n        addAtom(fixedSide, leftH, sphereGeoHydrogen, matHydrogen, \"H\");\n\n        cylinderBetween(fixedSide, c1, leftCl, 0.055, matSingleBond);\n        cylinderBetween(fixedSide, c1, leftH, 0.045, matSingleBond);\n\n        var rightCl = new 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resetBtn.addEventListener(\"click\", function(){\n            resetModel();\n          });\n        }\n\n        function resizeRenderer(){\n          var rect = canvas.getBoundingClientRect();\n          var width = Math.max(1, Math.floor(rect.width));\n          var height = Math.max(1, Math.floor(rect.height));\n\n          if (canvas.width !== width * renderer.getPixelRatio()) {\n            renderer.setSize(width, height, false);\n            camera.aspect = width \/ height;\n            camera.updateProjectionMatrix();\n          }\n        }\n\n        var isCanvasVisible = false;\n        var animationFrameId = null;\n\n        function startAnimationLoop(){\n          if (animationFrameId === null) {\n            animationFrameId = requestAnimationFrame(animate);\n          }\n        }\n\n        function stopAnimationLoop(){\n          if (animationFrameId !== null) {\n            cancelAnimationFrame(animationFrameId);\n            animationFrameId = null;\n          }\n        }\n\n        function animate(){\n          if (!isCanvasVisible) {\n            animationFrameId = null;\n            return;\n          }\n\n          animationFrameId = requestAnimationFrame(animate);\n          resizeRenderer();\n\n          sceneRotX = sceneRotX + (targetRotX - sceneRotX) * 0.08;\n          sceneRotY = sceneRotY + (targetRotY - sceneRotY) * 0.08;\n\n          molecule.rotation.x = sceneRotX;\n          molecule.rotation.y = sceneRotY;\n\n          camera.position.z = zoomDistance;\n          camera.lookAt(0, 0, 0);\n\n          if (restrictedAnimActive) {\n            rotationAngle = rotationAngle + rotationVelocity;\n\n            if (!attemptBounced) {\n              rotationVelocity = rotationVelocity * 0.985;\n\n              if (rotationAngle > 0.34) {\n                rotationVelocity = -0.145;\n                attemptBounced = true;\n                flashValue = 1;\n                shakeValue = 1;\n              }\n            } else {\n              rotationVelocity = rotationVelocity + (-rotationAngle) * 0.08;\n              rotationVelocity = rotationVelocity * 0.88;\n\n              if (Math.abs(rotationAngle) < 0.006) {\n                if (Math.abs(rotationVelocity) < 0.006) {\n                  rotationAngle = 0;\n                  rotationVelocity = 0;\n                  restrictedAnimActive = false;\n                  attemptBounced = false;\n\n                  if (rotateBtn) {\n                    rotateBtn.classList.remove(\"is-active\");\n                  }\n                }\n              }\n            }\n\n            rotatingSide.rotation.x = rotationAngle;\n          } else {\n            rotatingSide.rotation.x = rotationAngle;\n          }\n\n          flashValue = flashValue * 0.94;\n          shakeValue = shakeValue * 0.9;\n\n          matDoubleBondA.color.copy(baseDoubleColor).lerp(alertDoubleColor, flashValue);\n          matDoubleBondB.color.copy(baseDoubleColor).lerp(alertDoubleColor, flashValue);\n\n          matDoubleBondA.emissiveIntensity = flashValue * 0.8;\n          matDoubleBondB.emissiveIntensity = flashValue * 0.8;\n\n          root.position.y = Math.sin(Date.now() * 0.03) * 0.03 * shakeValue;\n\n          renderer.render(scene, camera);\n        }\n\n        function setCanvasVisibility(isVisible){\n          isCanvasVisible = isVisible;\n\n          if (isCanvasVisible) {\n            startAnimationLoop();\n          } else {\n            stopAnimationLoop();\n          }\n        }\n\n        if (\"IntersectionObserver\" in window) {\n          var piObserver = new IntersectionObserver(function(entries){\n            setCanvasVisibility(entries[0].isIntersecting);\n          }, {\n            threshold: 0.05\n          });\n\n          piObserver.observe(canvas);\n        } else {\n          setCanvasVisibility(true);\n        }\n      }\n\n      document.addEventListener(\"DOMContentLoaded\", function(){\n        loadThreeShared(startPiModel);\n      });\n    })();\n  <\/script>\n<\/div>\n\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">4<\/div><h2>Assigning E and Z<\/h2><\/div>\n        <p>To name an alkene with E-Z stereoisomerism, first identify the <strong>priority group<\/strong> on each carbon atom of the double bond.<\/p>\n        <p>The priority group is found by comparing the atoms directly attached to each double-bond carbon. The atom with the <strong>higher atomic number<\/strong> has higher priority.<\/p>\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Arrangement of priority groups<\/th>\n                <th>Name used<\/th>\n                <th>Memory aid<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td>Priority groups on the same side of the C=C bond<\/td>\n                <td><strong>Z<\/strong><\/td>\n                <td><strong>Z<\/strong> comes from <em>zusammen<\/em>, meaning together.<\/td>\n              <\/tr>\n              <tr>\n                <td>Priority groups on opposite sides of the C=C bond<\/td>\n                <td><strong>E<\/strong><\/td>\n                <td><strong>E<\/strong> comes from <em>entgegen<\/em>, meaning opposite.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n        <div class=\"ols-figure-card ols-zoom-pop\">\n          <div class=\"ols-figure-image\">\n            <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/T5.2-dichloroetheneisomers.webp\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/T5.2-dichloroetheneisomers.webp\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/T5.2-dichloroetheneisomers.webp\" alt=\"E\/Z isomers of dichloroethene explained\"><\/a>\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\">5<\/div><h2>Cis-Trans Isomerism<\/h2><\/div>\n        <p><strong>Cis-trans isomerism<\/strong> is a simpler special case of E-Z isomerism. It can be used when two of the substituent groups attached to the double bond are identical.<\/p>\n        <p>For but-2-ene, the two CH<sub>3<\/sub> groups can be on the same side or on opposite sides of the double bond.<\/p>\n        <div class=\"ols-comparison-grid\">\n          <div class=\"ols-mini-card ols-zoom-pop\">\n            <div class=\"ols-mini-card-image\">\n              <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/z-but-2-ene.webp\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/z-but-2-ene.webp\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/z-but-2-ene.webp\" alt=\"Chemical structure of z-but-2-ene\"><\/a>\n            <\/div>\n            <div class=\"ols-mini-card-body\">\n              <h3>Z-but-2-ene<\/h3>\n              <p>The two CH<sub>3<\/sub> groups are on the same side, so this can also be called <strong>cis-but-2-ene<\/strong>.<\/p>\n            <\/div>\n          <\/div>\n          <div class=\"ols-mini-card ols-zoom-pop\">\n            <div class=\"ols-mini-card-image\">\n              <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/e-but-2-ene.webp\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/e-but-2-ene.webp\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/e-but-2-ene.webp\" alt=\"Chemical structure of but-2-ene\"><\/a>\n            <\/div>\n            <div class=\"ols-mini-card-body\">\n              <h3>E-but-2-ene<\/h3>\n              <p>The two CH<sub>3<\/sub> groups are on opposite sides, so this can also be called <strong>trans-but-2-ene<\/strong>.<\/p>\n            <\/div>\n          <\/div>\n        <\/div>\n        <div class=\"ols-key-box\"><p><strong>Important:<\/strong> E-Z notation is the more general and accurate naming system, especially when the groups attached to the C=C bond are not identical.<\/p><\/div>\n      <\/article>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\"><div class=\"ols-note-icon\">6<\/div><h2>Common Exam Mistakes<\/h2><\/div>\n        <ul>\n          <li>Do not call E-Z isomers <strong>structural isomers<\/strong>. They have the same structural formula.<\/li>\n          <li>Do not assign E or Z by only looking at the largest group visually. Use <strong>atomic number priority<\/strong>.<\/li>\n          <li>Do not assume every alkene shows E-Z isomerism. Each carbon in the C=C bond must have two different groups attached.<\/li>\n          <li>Do not say the molecule rotates around the double bond. The whole point is that rotation around C=C is restricted.<\/li>\n        <\/ul>\n      <\/article>\n\n      <section class=\"ols-h5p-card\">\n        <h2>Check Your Understanding<\/h2>\n        <p>Use these short activities to check the key ideas before moving on to electrophilic addition.<\/p>\n\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-17\" class=\"h5p-iframe\" data-content-id=\"17\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Geometric Isomerism: Key Concepts Check\"><\/iframe><\/div><\/div>\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-18\" class=\"h5p-iframe\" data-content-id=\"18\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Geometric Isomerism: Conditions for E-Z Isomerism\"><\/iframe><\/div><\/div>\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-19\" class=\"h5p-iframe\" data-content-id=\"19\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Geometric Isomerism: Why But-1-ene Does Not Show E-Z\"><\/iframe><\/div><\/div>\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-20\" class=\"h5p-iframe\" data-content-id=\"20\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Geometric Isomerism: Assigning E and Z\"><\/iframe><\/div><\/div>\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-297\" class=\"h5p-iframe\" data-content-id=\"297\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Alkene that exists as E-Z isomers\"><\/iframe><\/div><\/div>\n      <\/section>\n\n      <section class=\"ols-infographic-full\" aria-label=\"Geometric isomerism infographic summary\">\n        <div class=\"ols-infographic-full-frame\">\n          <a class=\"ols-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Geometric-Isomerism-infographic.webp\" onclick=\"if(window.olsGeoFull){return window.olsGeoFull(this);}return true;\"><img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Geometric-Isomerism-infographic.webp\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Geometric-Isomerism-infographic.webp\" alt=\"Geometric isomerism summary showing stereoisomerism, restricted rotation, E-Z naming, priority groups and cis-trans isomerism\"><\/a>\n        <\/div>\n      <\/section>\n\n\n\n<section class=\"ols-related-card\">\n        <h2>Related Alkene Revision Notes<\/h2>\n        <p>Continue through Topic 6 by linking geometric isomerism to alkene bonding, electrophilic addition and polymerisation.<\/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\/topic-6-organic-chemistry-i\/alkenes\/alkene-bonding\/\">Alkene Bonding<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/electrophilic-addition-mechanism\/\">Electrophilic Addition Mechanism<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/\">Reactions of Alkenes<\/a>\n        <\/div>\n      <\/section>\n\n\n            <section class=\"ols-course-cta-alkenes\" id=\"olsCourseCtaAlkenes001\">\r\n  <style>\r\n    .ols-course-cta-alkenes,\r\n    .ols-course-cta-alkenes * {\r\n      box-sizing: border-box;\r\n    }\r\n\r\n    .ols-course-cta-alkenes {\r\n      --navy: #1C244B;\r\n      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.ols-course-cta-alkenes .ols-course-cta-card {\r\n        padding: 20px;\r\n        border-radius: 24px;\r\n      }\r\n\r\n      .ols-course-cta-alkenes .ols-course-cta-header-row {\r\n        align-items: stretch;\r\n      }\r\n\r\n      .ols-course-cta-alkenes .ols-course-button-top {\r\n        width: 100%;\r\n      }\r\n\r\n      .ols-course-cta-alkenes .ols-course-cta-stats,\r\n      .ols-course-cta-alkenes .ols-course-cta-features {\r\n        grid-template-columns: 1fr;\r\n      }\r\n\r\n      .ols-course-cta-alkenes .ols-course-animation-wrap {\r\n        padding: 0;\r\n        border-radius: 0;\r\n      }\r\n\r\n      .ols-course-cta-alkenes .ols-animation-frame-shell {\r\n        height: 420px;\r\n        border-radius: 18px;\r\n      }\r\n\r\n      .ols-course-cta-alkenes .ols-animation-play-circle {\r\n        width: 76px;\r\n        height: 76px;\r\n      }\r\n\r\n      .ols-course-cta-alkenes .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-alkenes .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-alkenes .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\/alkenes-topic-6c-edexcel-a-level-chemistry\/\" aria-label=\"Open the Edexcel A Level Chemistry Topic 6C Alkenes 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\/04\/edexcel-a-level-chemistry-topic-6c-alkenes-interactive-course-banner.jpg\"\r\n            alt=\"Edexcel A Level Chemistry Topic 6C Alkenes 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            Paper 2 | 9CH0\/02 | Topic 6C Alkenes Course\r\n          <\/div>\r\n\r\n          <a class=\"ols-course-button ols-course-button-top\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/alkenes-topic-6c-edexcel-a-level-chemistry\/\">\r\n            View Course\r\n          <\/a>\r\n\r\n        <\/div>\r\n\r\n        <h2>\r\n          Master Alkenes for Edexcel 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 6C Alkenes course, with guided video teaching, diagnostic MCQ practice, teacher-marked short-answer questions and a specification assignment with a personalised progress report.\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>Guided learning<\/span>\r\n          <strong>12 hours<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>Video lessons<\/span>\r\n          <strong>145 mins<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>MCQ practice<\/span>\r\n          <strong>41 marks<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>SAQ practice<\/span>\r\n          <strong>244 marks<\/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 6C 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\/alkenes-topic-6c-edexcel-a-level-chemistry\/\">\r\n        View Alkenes Topic 6C 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  animation:olsMcqScreenEnter 1s ease forwards;\r\n}\r\n\r\n@keyframes olsMcqScreenEnter{\r\n  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.mcq-question-area{\r\n  background:#eaf0ff;\r\n  padding:28px 30px 30px;\r\n  position:relative;\r\n  height:610px;\r\n}\r\n\r\n.mcq-question-lead{\r\n  margin:0 0 14px;\r\n  font-size:24px;\r\n  line-height:1.35;\r\n  color:#111827;\r\n}\r\n\r\n.mcq-ionic-table{\r\n  border-collapse:collapse;\r\n  width:500px;\r\n  margin-bottom:8px;\r\n  font-size:21px;\r\n  color:#111827;\r\n}\r\n\r\n.mcq-ionic-table th,\r\n.mcq-ionic-table td{\r\n  border:1.5px solid #c9ced8;\r\n  padding:12px 18px;\r\n  text-align:center;\r\n}\r\n\r\n.mcq-ionic-table th{\r\n  background:#f2f2f2;\r\n  font-weight:700;\r\n}\r\n\r\n.mcq-ionic-table td{\r\n  background:#eaf0ff;\r\n}\r\n\r\n.mcq-question-main{\r\n  margin:6px 0 28px;\r\n  font-size:24px;\r\n  line-height:1.35;\r\n  color:#111827;\r\n}\r\n\r\n.mcq-options-wrap{\r\n  display:flex;\r\n  flex-direction:column;\r\n  gap:17px;\r\n  max-width:1200px;\r\n}\r\n\r\n.mcq-option-row{\r\n  display:flex;\r\n  align-items:center;\r\n  min-height:34px;\r\n  position:relative;\r\n}\r\n\r\n.mcq-radio{\r\n  width:28px;\r\n  height:28px;\r\n  border-radius:50%;\r\n  border:2px solid #6b7280;\r\n  margin-right:16px;\r\n  background:transparent;\r\n  position:relative;\r\n  flex:0 0 auto;\r\n}\r\n\r\n.mcq-radio::after{\r\n  content:\"\";\r\n  position:absolute;\r\n  inset:5px;\r\n  border-radius:50%;\r\n  background:#6b7280;\r\n  opacity:0;\r\n  transform:scale(0.4);\r\n  transition:opacity 0.25s ease,transform 0.25s ease;\r\n}\r\n\r\n.mcq-option-row.selected .mcq-radio::after{\r\n  opacity:1;\r\n  transform:scale(1);\r\n}\r\n\r\n.mcq-radio-ripple{\r\n  position:absolute;\r\n  left:14px;\r\n  top:50%;\r\n  width:28px;\r\n  height:28px;\r\n  border-radius:50%;\r\n  border:2px solid rgba(28,36,75,0.28);\r\n  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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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the ions can get closer together.\\n\"+\r\n\"\u2022 Smaller ions \u2192 stronger electrostatic attraction \u2192 stronger ionic lattice.\\n\"+\r\n\"\u2022 Na\u207a (0.102 nm) is smaller than K\u207a (0.138 nm).\\n\"+\r\n\"\u2022 F\u207b (0.133 nm) is smaller than Cl\u207b (0.180 nm).\\n\\n\"+\r\n\"Therefore, the strongest ionic bonding occurs in the compound formed by the smallest cation and the smallest anion \u2192 sodium fluoride (NaF).\\n\\n\"+\r\n\"The correct answer is: sodium fluoride\";\r\n\r\nconst mcqIntroScreen=document.getElementById(\"mcqIntroScreen\");\r\nconst mcqIntroTitleText=document.getElementById(\"mcqIntroTitleText\");\r\nconst mcqIntroTitleCursor=document.getElementById(\"mcqIntroTitleCursor\");\r\nconst mcqScreen=document.getElementById(\"mcqScreen\");\r\nconst mcqWrongOption=document.getElementById(\"mcqWrongOption\");\r\nconst mcqSubmitButton=document.getElementById(\"mcqSubmitButton\");\r\nconst 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If the higher priority groups are on opposite sides, the isomer is E.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"What is the difference between E-Z and cis-trans isomerism?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"Cis-trans naming is useful when comparing identical or directly comparable groups across a double bond, while E-Z notation is more general because it uses priority rules based on atomic number.\"\n          }\n        }\n      ]\n    }\n  ]\n}\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>Revision Notes \/ A Level Chemistry \/ Edexcel \/ Topic 6 Organic Chemistry I \/ Alkenes \/ Geometric Isomerism Geometric Isomerism A concise revision guide to stereoisomerism in alkenes, restricted rotation around C=C bonds, E-Z naming, priority groups and the link between E-Z and cis-trans isomerism. Paper 2 Topic 6: Organic Chemistry I 9CH0\/02 Written [&hellip;]<\/p>\n","protected":false},"author":12,"featured_media":0,"parent":4694,"menu_order":1,"comment_status":"closed","ping_status":"closed","template":"","meta":{"productId":0,"courseId":0,"footnotes":""},"class_list":["post-4839","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/4839","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/comments?post=4839"}],"version-history":[{"count":0,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/4839\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/4694"}],"wp:attachment":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/media?parent=4839"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}