{"id":7159,"date":"2026-09-08T17:56:47","date_gmt":"2026-09-08T16:56:47","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/?page_id=7159"},"modified":"2026-09-22T08:04:59","modified_gmt":"2026-09-22T07:04:59","slug":"electrophilic-addition-mechanism","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/electrophilic-addition-mechanism\/","title":{"rendered":"Electrophilic Addition Mechanism"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-electrophilic-addition-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      --grey-text: #667085;\n      --body-text: #1f2937;\n      --border: rgba(28, 36, 75, 0.14);\n      --shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      --inner-shadow: 0 10px 26px 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     <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/producing-alkenes\/\">Producing Alkenes<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/electrophilic-addition-mechanism\/\">Electrophilic Addition Mechanism<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/markovnikov-addition\/\">Markovnikov Addition<\/a><\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/reactions-of-alkenes\/\">Reactions of Alkenes<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/reactions-of-alkenes\/hydrogen\/\">Hydrogen<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/reactions-of-alkenes\/halogens\/\">Halogens<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/reactions-of-alkenes\/bromine-water\/\">Bromine Water<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/reactions-of-alkenes\/hydrogen-halide\/\">Hydrogen Halide<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/reactions-of-alkenes\/steam\/\">Steam<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/reactions-of-alkenes\/kmno4\/\">KMnO4<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/reactions-of-alkenes\/oxidative-cleavage\/\">Oxidative Cleavage<\/a><\/li>\n        <\/ul>\n      <\/li>\n    <\/ul>\n  <\/div>\n  <div class=\"ols-topic-group\">\n    <h4>Other Topics<\/h4>\n    <ul class=\"ols-topic-list\">\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/\">Topic 14 overview<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkanes\/\">14.1 Alkanes<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-13-an-introduction-to-as-level-organic-chemistry\/\">Topic 13 Introduction to AS Organic Chemistry<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-20-polymerisation\/\">Topic 20 Polymerisation<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-15-halogen-compounds\/\">Topic 15 Halogen Compounds<\/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 = document.querySelector('.ols-sidebar');\r\n    if (!sidebar) return false;\r\n\r\n    var currentPath = 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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-14-hydrocarbons\/\">Topic 14 Hydrocarbons<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/\">Alkenes<\/a> \/\n<span>Electrophilic Addition Mechanism<\/span>\n<\/nav>\n\n    <header class=\"ols-title-card\">\n      <h1>Electrophilic Addition Mechanism<\/h1>\n      <p class=\"ols-page-intro\">A concise revision guide to addition reactions of alkenes, electrophiles, electron-rich \u03c0 bonds and why the carbon-carbon double bond is the reactive centre in alkene chemistry.<\/p>\n\n      <div class=\"ols-badges\">\n        <div class=\"ols-badge\">AS Level<\/div>\n<div class=\"ols-badge\">Topic 14: Hydrocarbons<\/div>\n<div class=\"ols-badge\">9701 Papers 1 and 2<\/div>\n      <\/div>\n\n      <div class=\"ols-author\">\n        <img decoding=\"async\" class=\"ols-author-avatar-img\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\" alt=\"Dr. Mohammed Al-Fatah\">\n        <div class=\"ols-author-content\">\n          <h2 class=\"ols-author-title\">Written by: Dr. Mohammed Al-Fatah<\/h2>\n          <p class=\"ols-author-description\">Chemistry specialist revision notes for A Level Chemistry.<\/p>\n          <a class=\"ols-linkedin-pill\" href=\"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\" target=\"_blank\" rel=\"noopener noreferrer\">\n            <svg class=\"ols-linkedin-icon\" viewBox=\"0 0 24 24\" fill=\"currentColor\" aria-hidden=\"true\">\n              <path d=\"M4.98 3.5C4.98 4.88 3.86 6 2.48 6S0 4.88 0 3.5 1.12 1 2.48 1s2.5 1.12 2.5 2.5zM.5 8h4V24h-4V8zm7 0h3.8v2.2h.1c.5-.9 1.8-2.2 3.9-2.2 4.2 0 5 2.8 5 6.4V24h-4v-7.6c0-1.8 0-4.2-2.6-4.2s-3 2-3 4v7.8h-4V8z\"><\/path>\n            <\/svg>\n            View LinkedIn Profile\n          <\/a>\n        <\/div>\n      <\/div>\n    <\/header>\n\n    <section class=\"ols-h5p-card ols-h5p-inline ols-h5p-recap\">\n<span class=\"ols-h5p-kicker\">Before you start<\/span>\n<h2>GCSE Recap: What Alkenes Do<\/h2>\n<p>Three quick questions on the reactions of alkenes that you met at GCSE.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"735\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n      <div class=\"ols-note-title\"><div class=\"ols-note-icon\">1<\/div><h2>Addition Reactions of Alkenes<\/h2><\/div>\n      <p>An <strong>addition reaction<\/strong> is a reaction in which two reactant molecules combine to form a single product molecule.<\/p>\n      <p>Alkenes commonly undergo addition reactions because their <strong>carbon-carbon double bond<\/strong> can be broken and replaced by new single bonds.<\/p>\n      <p>This is why the C=C bond is the functional group that controls the characteristic reactions of alkenes.<\/p>\n      <div class=\"ols-key-box\"><p><strong>Key idea:<\/strong> In an alkene addition reaction, atoms add across the C=C double bond and only one organic product molecule is formed.<\/p><\/div>\n      <div class=\"ols-figure-card\">\n        <div class=\"ols-figure-image\" role=\"img\" aria-label=\"Addition reaction diagram showing an alkene double bond opening to form a saturated product\">\n          <svg viewBox=\"0 0 900 360\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\">\n            <rect width=\"900\" height=\"360\" rx=\"28\" fill=\"#ffffff\"><\/rect>\n            <rect x=\"38\" y=\"42\" width=\"260\" height=\"236\" rx=\"24\" fill=\"#eef4ff\" stroke=\"#d8e5ff\"><\/rect>\n            <rect x=\"600\" y=\"42\" width=\"260\" height=\"236\" rx=\"24\" fill=\"#fff7f7\" stroke=\"#f4dada\"><\/rect>\n            <text x=\"168\" y=\"88\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"26\" font-weight=\"800\" fill=\"#1C244B\">Alkene<\/text>\n            <text x=\"730\" y=\"88\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"26\" font-weight=\"800\" fill=\"#1C244B\">Addition product<\/text>\n            <line x1=\"118\" y1=\"166\" x2=\"218\" y2=\"166\" stroke=\"#1C244B\" stroke-width=\"10\" stroke-linecap=\"round\"><\/line>\n            <line x1=\"118\" y1=\"188\" x2=\"218\" y2=\"188\" stroke=\"#2563eb\" stroke-width=\"10\" stroke-linecap=\"round\"><\/line>\n            <text x=\"168\" y=\"235\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"28\" font-weight=\"700\" fill=\"#1C244B\">C=C<\/text>\n            <line x1=\"365\" y1=\"176\" x2=\"535\" y2=\"176\" stroke=\"#1C244B\" stroke-width=\"6\" stroke-linecap=\"round\"><\/line>\n            <polygon points=\"535,176 510,160 510,192\" fill=\"#1C244B\"><\/polygon>\n            <text x=\"450\" y=\"138\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"23\" font-weight=\"700\" fill=\"#2563eb\">two reactants<\/text>\n            <text x=\"450\" y=\"225\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"23\" font-weight=\"700\" fill=\"#2563eb\">one product<\/text>\n            <line x1=\"680\" y1=\"176\" x2=\"780\" y2=\"176\" stroke=\"#1C244B\" stroke-width=\"10\" stroke-linecap=\"round\"><\/line>\n            <circle cx=\"660\" cy=\"176\" r=\"22\" fill=\"#2563eb\"><\/circle>\n            <circle cx=\"800\" cy=\"176\" r=\"22\" fill=\"#2563eb\"><\/circle>\n            <text x=\"660\" y=\"184\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"18\" font-weight=\"800\" fill=\"#ffffff\">X<\/text>\n            <text x=\"800\" y=\"184\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"18\" font-weight=\"800\" fill=\"#ffffff\">Y<\/text>\n            <text x=\"730\" y=\"235\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"25\" font-weight=\"700\" fill=\"#1C244B\">new single bonds<\/text>\n          <\/svg>\n        <\/div>\n        <div class=\"ols-figure-caption\">\n          <h3>Addition across a double bond<\/h3>\n          <p>The double bond opens up, allowing new atoms or groups to attach to the two carbon atoms from the original C=C bond.<\/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: Addition or Not?<\/h2>\n<p>Decide quickly whether each equation shows an addition reaction.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-24\" class=\"h5p-iframe\" data-content-id=\"24\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition Quick-Fire: Addition or Not Addition\"><\/iframe><\/div><\/div>\n<\/section>\n\n    <article class=\"ols-note-card\">\n      <div class=\"ols-note-title\"><div class=\"ols-note-icon\">2<\/div><h2>Why the \u03c0 Bond Reacts<\/h2><\/div>\n      <p>In an alkene, the <strong>\u03c0 bond is weaker than the \u03c3 bond<\/strong>, so it requires less energy to break during a reaction.<\/p>\n      <p>The \u03c0 bond also contains a region of <strong>high electron density<\/strong>. This exposed electron density is especially attractive to electron-seeking species.<\/p>\n      <p>Because the \u03c0 bond is both weaker and more exposed than a \u03c3 bond, it is particularly susceptible to attack by electrophiles.<\/p>\n      <div class=\"ols-key-box\"><p><strong>Exam focus:<\/strong> Link alkene reactivity to the exposed, electron-rich \u03c0 bond rather than simply saying that alkenes have a double bond.<\/p><\/div>\n      <div class=\"ols-figure-card\">\n        <div class=\"ols-figure-image\" role=\"img\" aria-label=\"Pi bond electron density diagram showing electron-rich regions above and below the carbon-carbon bond\">\n          <svg viewBox=\"0 0 900 390\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\">\n            <rect width=\"900\" height=\"390\" rx=\"28\" fill=\"#ffffff\"><\/rect>\n            <ellipse cx=\"450\" cy=\"124\" rx=\"250\" ry=\"62\" fill=\"#2563eb\" opacity=\"0.18\"><\/ellipse>\n            <ellipse cx=\"450\" cy=\"266\" rx=\"250\" ry=\"62\" fill=\"#2563eb\" opacity=\"0.18\"><\/ellipse>\n            <ellipse cx=\"450\" cy=\"124\" rx=\"172\" ry=\"42\" fill=\"#2563eb\" opacity=\"0.26\"><\/ellipse>\n            <ellipse cx=\"450\" cy=\"266\" rx=\"172\" ry=\"42\" fill=\"#2563eb\" opacity=\"0.26\"><\/ellipse>\n            <circle cx=\"355\" cy=\"195\" r=\"40\" fill=\"#1C244B\"><\/circle>\n            <circle cx=\"545\" cy=\"195\" r=\"40\" fill=\"#1C244B\"><\/circle>\n            <text x=\"355\" y=\"205\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"30\" font-weight=\"800\" fill=\"#ffffff\">C<\/text>\n            <text x=\"545\" y=\"205\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"30\" font-weight=\"800\" fill=\"#ffffff\">C<\/text>\n            <line x1=\"395\" y1=\"183\" x2=\"505\" y2=\"183\" stroke=\"#1C244B\" stroke-width=\"10\" stroke-linecap=\"round\"><\/line>\n            <line x1=\"395\" y1=\"207\" x2=\"505\" y2=\"207\" stroke=\"#2563eb\" stroke-width=\"10\" stroke-linecap=\"round\"><\/line>\n            <text x=\"450\" y=\"60\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"28\" font-weight=\"800\" fill=\"#1C244B\">exposed \u03c0 electron density<\/text>\n            <text x=\"450\" y=\"350\" text-anchor=\"middle\" font-family=\"Poppins, Arial\" font-size=\"24\" font-weight=\"700\" fill=\"#667085\">weaker than the \u03c3 bond and easier to break<\/text>\n            <path d=\"M712 112 C660 126, 632 154, 602 180\" fill=\"none\" stroke=\"#c81e1e\" stroke-width=\"6\" stroke-linecap=\"round\"><\/path>\n            <polygon points=\"602,180 612,154 626,177\" fill=\"#c81e1e\"><\/polygon>\n            <text x=\"744\" y=\"105\" font-family=\"Poppins, Arial\" font-size=\"22\" font-weight=\"800\" fill=\"#c81e1e\">E\u207a<\/text>\n          <\/svg>\n        <\/div>\n        <div class=\"ols-figure-caption\">\n          <h3>Electron-rich \u03c0 bond<\/h3>\n          <p>The \u03c0 bond forms exposed electron density above and below the molecular plane, making the alkene attractive to electrophiles.<\/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: Spot the Errors<\/h2>\n<p>Click the five wrong words in a student&#039;s description of the \u03c0 bond.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-22\" class=\"h5p-iframe\" data-content-id=\"22\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition Mark the Words: Errors About the \u03c0 Bond\"><\/iframe><\/div><\/div>\n<\/section>\n\n    <article class=\"ols-note-card purple\">\n      <div class=\"ols-note-title\"><div class=\"ols-note-icon\">3<\/div><h2>Electrophiles<\/h2><\/div>\n      <p>An <strong>electrophile<\/strong> is an <strong>electron pair acceptor<\/strong>.<\/p>\n      <p>Electrophiles are attracted to regions of high electron density. In alkenes, this means the electrophile is drawn towards the electron-rich \u03c0 bond.<\/p>\n      <p>This attraction begins the electrophilic addition mechanism.<\/p>\n      <div class=\"ols-definition-box\">\n        <div class=\"ols-definition-circle\">E\u207a<\/div>\n        <p><strong>Electrophile:<\/strong> A species that accepts an electron pair from an electron-rich region during a chemical reaction.<\/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: Find the Electrophile<\/h2>\n<p>Identify the electrophile in a reagent that this page has not used.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-23\" class=\"h5p-iframe\" data-content-id=\"23\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition MCQ: The Electrophile in Hydrogen Chloride\"><\/iframe><\/div><\/div>\n<\/section>\n\n    <article class=\"ols-note-card\">\n      <div class=\"ols-note-title\"><div class=\"ols-note-icon\">4<\/div><h2>The Electrophilic Addition Mechanism<\/h2><\/div>\n      <p>In electrophilic addition, the \u03c0 bond breaks and new single bonds are formed. The electrophile accepts an electron pair from the alkene.<\/p>\n      <p>At this stage, students must be careful with curly arrows. A curly arrow shows the movement of an <strong>electron pair<\/strong>, so the arrow should start from a bond or lone pair, not from a positive charge.<\/p>\n      <div class=\"ols-mechanism-grid\">\n        <div class=\"ols-mech-step\"><h3>1. Attraction<\/h3><p>The electrophile is attracted to the high electron density in the \u03c0 bond.<\/p><\/div>\n        <div class=\"ols-mech-step\"><h3>2. Bond breaking<\/h3><p>The \u03c0 bond breaks because it is weaker than the \u03c3 bond.<\/p><\/div>\n        <div class=\"ols-mech-step\"><h3>3. New bonds form<\/h3><p>New single bonds form to give an addition product.<\/p><\/div>\n      <\/div>\n      <div class=\"ols-key-box\"><p><strong>Remember:<\/strong> Electrophilic addition happens because the \u03c0 bond is electron-rich, exposed and relatively easy to break.<\/p><\/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: Order the Mechanism<\/h2>\n<p>Put the events of an electrophilic addition you have not seen into the correct order.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-21\" class=\"h5p-iframe\" data-content-id=\"21\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition Sort: Hydrogen Chloride with But-2-ene\"><\/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: Hydrogen Iodide and Cyclohexene<\/h2>\n<p>In each round, pick the one accurate statement about this addition.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-736\" class=\"h5p-iframe\" data-content-id=\"736\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition Summary: Hydrogen Iodide with Cyclohexene\"><\/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\">5<\/div>\n<h2>The Inductive Effect and Markovnikov Addition<\/h2>\n<\/div>\n<p>This section is the summary; the full explanation with worked examples is on the <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/markovnikov-addition\/\">Markovnikov Addition and the Inductive Effect<\/a> page.<\/p>\n<p>Cambridge asks you to describe and explain the <strong>inductive effect<\/strong> of alkyl groups on the stability of the carbocations formed during electrophilic addition, and to use this to explain <strong>Markovnikov addition<\/strong>.<\/p>\n<p>An alkyl group is <strong>electron-releasing<\/strong>: it pushes electron density along the \u03c3 bond towards the positively charged carbon. This spreads out and reduces the positive charge, which stabilises the carbocation. The more alkyl groups attached to the positive carbon, the greater the stabilisation.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Carbocation<\/th><th>Alkyl groups on C<sup>+<\/sup><\/th><th>Inductive stabilisation<\/th><th>Relative stability<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Primary<\/strong><\/td><td>one<\/td><td>least<\/td><td>lowest<\/td><\/tr>\n<tr><td><strong>Secondary<\/strong><\/td><td>two<\/td><td>more<\/td><td>intermediate<\/td><\/tr>\n<tr><td><strong>Tertiary<\/strong><\/td><td>three<\/td><td>most<\/td><td>highest<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>When a hydrogen halide such as HBr adds to an unsymmetrical alkene such as propene, two carbocations are possible. The reaction proceeds mainly through the <strong>more stable secondary carbocation<\/strong>, so the hydrogen atom ends up on the carbon that already carried more hydrogen atoms and bromine adds to the other carbon. This is Markovnikov addition, and 2-bromopropane is the major product.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Exam focus:<\/strong> Explain the major product by comparing carbocation stability and naming the inductive effect of the alkyl groups. Cambridge expects the mechanism to be drawn for bromine with ethene and for hydrogen bromide with propene.<\/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: Predict the Major Product<\/h2>\n<p>Use carbocation stability to predict the products from alkenes other than propene.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-739\" class=\"h5p-iframe\" data-content-id=\"739\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition Quick-Fire: Markovnikov Products from New Alkenes\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n      <div class=\"ols-note-title\"><div class=\"ols-note-icon\">6<\/div><h2>Exam Link: Why Alkenes React This Way<\/h2><\/div>\n      <p>Exam answers should connect three ideas: the alkene contains a C=C bond, the \u03c0 bond has high electron density, and electrophiles are attracted to this electron-rich region.<\/p>\n      <p>It is not enough to write that alkenes are reactive because they have a double bond. The explanation needs to identify the role of the \u03c0 bond and the electrophile.<\/p>\n      <div class=\"ols-table-wrap\">\n        <table class=\"ols-table\">\n          <thead>\n            <tr><th>Exam phrase<\/th><th>Why it matters<\/th><th>Common mistake to avoid<\/th><\/tr>\n          <\/thead>\n          <tbody>\n            <tr><td><strong>\u03c0 bond has high electron density<\/strong><\/td><td>Explains why an electrophile is attracted to the alkene.<\/td><td>Only saying that the double bond is reactive.<\/td><\/tr>\n            <tr><td><strong>Electrophile accepts an electron pair<\/strong><\/td><td>Links the definition of electrophile to the mechanism.<\/td><td>Calling the electrophile an electron donor.<\/td><\/tr>\n            <tr><td><strong>\u03c0 bond breaks and new single bonds form<\/strong><\/td><td>Explains why the reaction is an addition reaction.<\/td><td>Describing substitution instead of addition.<\/td><\/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: Explain Why the Alkene Reacts<\/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-740\" class=\"h5p-iframe\" data-content-id=\"740\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Electrophilic Addition Explain: Hex-3-ene Reacts but Hexane Does Not\"><\/iframe><\/div><\/div>\n<\/section>\n\n    \n\n    <section class=\"ols-infographic-full\" aria-label=\"Electrophilic addition mechanism visual summary\">\n      <a class=\"ols-infographic-full-frame\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Electrophilic-addition-reaction-overview.webp\" target=\"_blank\" rel=\"noopener noreferrer\" aria-label=\"Open electrophilic addition mechanism infographic full size\">\n        <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Electrophilic-addition-reaction-overview.webp\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Electrophilic-addition-reaction-overview.webp\" alt=\"Electrophilic addition reaction explained visually.\">\n      <\/a>\n    <\/section>\n\n    <section class=\"ols-related-card\">\n      <h2>Related Alkene Revision Notes<\/h2>\n      <p>Continue through CIE Topic 14 by linking electrophilic addition to alkene bonding, geometric isomerism and reactions of alkenes.<\/p>\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-14-hydrocarbons\/alkenes\/markovnikov-addition\/\">Markovnikov Addition<\/a>\n        <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-13-an-introduction-to-as-level-organic-chemistry\/shapes-of-organic-molecules\/alkene-bonding\/\">Alkene Bonding<\/a>\n        <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-13-an-introduction-to-as-level-organic-chemistry\/isomerism\/geometric-isomerism\/\">Geometric Isomerism<\/a>\n        <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-14-hydrocarbons\/alkenes\/reactions-of-alkenes\/\">Reactions of Alkenes<\/a>\n      <\/div>\n    <\/section>\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      --blue: #2563eb;\r\n    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.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-alkenes .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-alkenes .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      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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-14-2-cambridge-international\/\" aria-label=\"Open the Cambridge International AS and A Level Chemistry Topic 14.2 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\/09\/cambridge-international-a-level-chemistry-topic-14-2-alkenes-interactive-course-banner-v2.jpg\"\r\n            alt=\"Cambridge International AS and A Level Chemistry Topic 14.2 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            Cambridge 9701 | Topic 14.2 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-14-2-cambridge-international\/\">\r\n            View Course\r\n          <\/a>\r\n\r\n        <\/div>\r\n\r\n        <h2>\r\n          Master Alkenes 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 14.2 Alkenes 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 14.2 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-14-2-cambridge-international\/\">\r\n        View Alkenes Topic 14.2 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  transform:translate(-50%,-50%) scale(1);\r\n  opacity:0;\r\n  pointer-events:none;\r\n}\r\n\r\n.mcq-option-row.clicking .mcq-radio-ripple{\r\n  animation:mcqRipple 0.75s ease forwards;\r\n}\r\n\r\n@keyframes mcqRipple{\r\n  0%{opacity:0.65;transform:translate(-50%,-50%) scale(1);}\r\n  100%{opacity:0;transform:translate(-50%,-50%) scale(2.5);}\r\n}\r\n\r\n.mcq-option-label{\r\n  font-size:23px;\r\n  color:#111827;\r\n}\r\n\r\n.mcq-specific-feedback{\r\n  display:inline-flex;\r\n  align-items:center;\r\n  margin-left:18px;\r\n  min-height:38px;\r\n  opacity:0;\r\n  transform:translateX(-8px);\r\n}\r\n\r\n.mcq-specific-feedback.show{\r\n  opacity:1;\r\n  transform:translateX(0);\r\n  transition:opacity 0.35s ease,transform 0.35s ease;\r\n}\r\n\r\n.mcq-cross-icon{\r\n  width:26px;\r\n  height:26px;\r\n  border-radius:50%;\r\n  border:2px solid #d83255;\r\n  color:#d83255;\r\n  display:inline-flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n  font-size:18px;\r\n  font-weight:700;\r\n  margin-right:12px;\r\n  opacity:0;\r\n  transform:scale(0.4);\r\n}\r\n\r\n.mcq-cross-icon.show{\r\n  animation:mcqCrossPop 0.35s ease forwards;\r\n}\r\n\r\n@keyframes mcqCrossPop{\r\n  70%{opacity:1;transform:scale(1.18);}\r\n  100%{opacity:1;transform:scale(1);}\r\n}\r\n\r\n.mcq-specific-feedback-text{\r\n  display:inline-block;\r\n  background:#fff4b8;\r\n  color:#111827;\r\n  padding:8px 16px;\r\n  font-size:22px;\r\n  line-height:1.35;\r\n  min-width:850px;\r\n  min-height:44px;\r\n}\r\n\r\n.mcq-submit-button{\r\n  position:absolute;\r\n  right:34px;\r\n  bottom:30px;\r\n  border:0;\r\n  border-radius:999px;\r\n  background:#1C244B;\r\n  color:#ffffff;\r\n  padding:14px 28px;\r\n  font-size:18px;\r\n  font-weight:600;\r\n  box-shadow:0 14px 32px rgba(28,36,75,0.25);\r\n  cursor:default;\r\n  transition:transform 0.2s ease,box-shadow 0.2s ease,background 0.2s ease;\r\n}\r\n\r\n.mcq-submit-button.clicked{\r\n  transform:translateY(2px) scale(0.97);\r\n  background:#26315f;\r\n  box-shadow:0 7px 18px rgba(28,36,75,0.22);\r\n}\r\n\r\n.mcq-general-feedback{\r\n  height:520px;\r\n  background:#fff3c9;\r\n  color:#8a6a00;\r\n  padding:26px 30px 28px;\r\n  font-size:23px;\r\n  line-height:1.34;\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.mcq-general-feedback.show{\r\n  opacity:1;\r\n  transform:translateY(0);\r\n}\r\n\r\n#mcqGeneralText{\r\n  white-space:pre-wrap;\r\n}\r\n\r\n.mcq-specific-cursor{background:#111827;}\r\n.mcq-general-cursor{background:#8a6a00;}\r\n\r\n.ols-saq-screen{\r\n  width:1360px;\r\n  height:965px;\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-saq-screen.show{\r\n  animation:olsSaqScreenEnter 1s ease forwards;\r\n}\r\n\r\n@keyframes olsSaqScreenEnter{\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.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  transform:translateY(0);\r\n}\r\n\r\n#saqTeacherText{\r\n  white-space:pre-wrap;\r\n}\r\n\r\n.saq-teacher-cursor{\r\n  background:#075f3b;\r\n}\r\n\r\n@media(max-width:900px){\r\n  .ols-video-title,\r\n  .ols-mcq-intro-title,\r\n  .ols-saq-intro-title{\r\n    font-size:clamp(42px,11vw,78px);\r\n    line-height:1.12;\r\n  }\r\n\r\n  .ols-title-cursor{\r\n    width:4px;\r\n    margin-left:6px;\r\n  }\r\n\r\n  .ols-video-card{\r\n    border-radius:20px;\r\n  }\r\n}\r\n<\/style>\r\n<\/head>\r\n\r\n<body>\r\n<div class=\"ols-combined-stage\">\r\n\r\n  <section id=\"sceneVideo\" class=\"ols-scene active\">\r\n    <div class=\"ols-video-stage\">\r\n      <div id=\"videoTitleScreen\" class=\"ols-video-title-screen\">\r\n        <div class=\"ols-video-title-wrap\">\r\n          <h1 class=\"ols-video-title\">\r\n            <span id=\"videoTitleText\"><\/span><span id=\"videoTitleCursor\" class=\"ols-title-cursor\"><\/span>\r\n          <\/h1>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <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 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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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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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