{"id":7696,"date":"2026-09-12T11:57:04","date_gmt":"2026-09-12T10:57:04","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/giant-covalent-structures\/"},"modified":"2026-09-26T10:32:17","modified_gmt":"2026-09-26T09:32:17","slug":"giant-covalent-structures","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/giant-covalent-structures\/","title":{"rendered":"Giant Covalent Structures"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-nature-of-covalent-bonding-9ch0-page\">\n  <style>\n    .ols-revision-page {\n      --navy: #1C244B;\n      --blue: #2563eb;\n      --soft-blue: #eef4ff;\n      --soft-red: #fff7f7;\n      --soft-purple: #f7f0ff;\n      --soft-green: #f0f7f1;\n      --soft-orange: #fff7ed;\n      --grey-text: #667085;\n      --body-text: 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border-radius: 22px; padding: 14px; margin: 18px 0 6px; }\n    .ols-figure-placeholder .ols-figure-caption p { margin: 10px 0 0; font-size: 14px; color: #667085; text-align: center; }\n<\/style>\n\n  <aside class=\"ols-sidebar\">\n  <div class=\"ols-sidebar-header\">\n    <h3>Revision Notes<\/h3>\n    <p>Cambridge International AS Level Chemistry<\/p>\n  <\/div>\n  <div class=\"ols-topic-group\">\n    <h4>3.4 Covalent Bonding<\/h4>\n    <ul class=\"ols-topic-list\">\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/\">Part overview<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/nature-of-covalent-bonding\/\">Nature of Covalent Bonding<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/dative-covalent-bonding\/\">Dative Covalent Bonding<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/giant-covalent-structures\/\">Giant Covalent Structures<\/a><\/li>\n<li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/sigma-and-pi-bonds-and-hybridisation\/\">Sigma and Pi Bonds and Hybridisation<\/a><\/li>\n<li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/bond-energy-and-bond-length\/\">Bond Energy and Bond Length<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/polar-molecules\/\">Non-Polar and Polar Molecules<\/a><\/li>\n    <\/ul>\n  <\/div>\n  <div class=\"ols-topic-group\">\n    <h4>Other Topic 3 Parts<\/h4>\n    <ul class=\"ols-topic-list\">\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/\">Topic 3 overview<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/electronegativity\/\">3.1 Electronegativity<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/shapes-of-molecules\/\">3.5 Shapes of Molecules<\/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  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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\/cie\/\">Cambridge International (CIE)<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/\">Topic 3 Chemical Bonding<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/covalent-bonding\/\">3.4 Covalent Bonding<\/a> \/\n<span>Giant Covalent Structures<\/span>\n<\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Giant Covalent Structures<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to giant covalent structures: how diamond, graphite and graphene are bonded, why their properties differ so much, and how the structure explains melting point, hardness and electrical conductivity.<\/p>\n\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">AS Level<\/div>\n<div class=\"ols-badge\">Topic 3: Chemical Bonding<\/div>\n<div class=\"ols-badge\">9701 Papers 1 and 2<\/div>\n        <\/div>\n\n        <div class=\"ols-author\">\n\n    <img decoding=\"async\"\n      class=\"ols-author-avatar-img\"\n      src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\"\n      alt=\"Dr. Mohammed Al-Fatah\"\n    >\n\n    <div class=\"ols-author-content\">\n\n      <h2 class=\"ols-author-title\">\n        Written by:<br><span>Dr. Mohammed Al-Fatah<\/span>\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      <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: Covalent Bonds and Small Molecules<\/h2>\n<p>Before you start, check three GCSE ideas that this page builds on.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"657\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">1<\/div>\n<h2>What Is a Giant Covalent Structure?<\/h2>\n<\/div>\n<p>In a <strong>giant covalent structure<\/strong> (also called a macromolecular or giant molecular structure) every atom is joined to its neighbours by <strong>strong covalent bonds<\/strong> that extend throughout the whole crystal. There are no separate molecules: a single crystal of diamond is, in effect, one enormous molecule. Compare this with a simple molecular substance such as iodine, where strong covalent bonds hold each I<sub>2<\/sub> molecule together but only weak intermolecular forces act between the molecules.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Feature<\/th><th>Giant covalent (diamond, graphite, graphene)<\/th><th>Simple molecular (iodine, ice, carbon dioxide)<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Particles<\/strong><\/td><td>Atoms in a continuous network<\/td><td>Discrete molecules<\/td><\/tr>\n<tr><td><strong>Forces broken on melting<\/strong><\/td><td>Strong covalent bonds<\/td><td>Weak intermolecular forces<\/td><\/tr>\n<tr><td><strong>Melting point<\/strong><\/td><td>Very high (diamond sublimes above 3600 \u00b0C)<\/td><td>Low<\/td><\/tr>\n<tr><td><strong>Solubility in water<\/strong><\/td><td>Insoluble<\/td><td>Usually low; some polar molecules dissolve<\/td><\/tr>\n<tr><td><strong>Electrical conductivity<\/strong><\/td><td>Usually none; graphite and graphene conduct<\/td><td>None<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> Melting a giant covalent structure means breaking covalent bonds, which needs a great deal of energy, so these substances have very high melting points and are hard or, in the case of graphite, strongly bonded within each layer.<\/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: Identify the Structure from Data<\/h2>\n<p>Use the data to decide which type of structure the solid has.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-440\" class=\"h5p-iframe\" data-content-id=\"440\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Giant Covalent Structures MCQ: Identifying the Structure from Data\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">2<\/div>\n<h2>Diamond<\/h2>\n<\/div>\n<p>In <strong>diamond<\/strong> each carbon atom forms <strong>four single covalent bonds<\/strong> to four other carbon atoms arranged <strong>tetrahedrally<\/strong> around it, with bond angles of 109.5\u00b0. The result is a rigid three-dimensional network in which every atom is locked in place by strong C-C bonds.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Property<\/th><th>Explanation from the structure<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Very high melting and sublimation point<\/strong><\/td><td>Many strong covalent bonds must be broken<\/td><\/tr>\n<tr><td><strong>Extremely hard<\/strong><\/td><td>The rigid tetrahedral network resists any distortion; diamond is used in cutting tools and drill tips<\/td><\/tr>\n<tr><td><strong>Does not conduct electricity<\/strong><\/td><td>All four outer electrons of each carbon are used in bonding, so there are no delocalised electrons<\/td><\/tr>\n<tr><td><strong>Insoluble in all solvents<\/strong><\/td><td>No solvent interaction can compete with the covalent bonds<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n\n<p><strong>Silicon<\/strong> has the same structure as diamond, which is why it is also a hard, high-melting solid, although its Si-Si bonds are weaker than C-C bonds. Silicon atoms are larger than carbon atoms, so the Si-Si bond is longer and the shared pair is further from both nuclei. This is why silicon melts at a lower temperature than diamond.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Exam sentence:<\/strong> Diamond has a giant covalent structure in which each carbon atom is bonded to four others by strong covalent bonds, so a large amount of energy is needed to break the bonds and it has a very high melting point.<\/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 Properties of Silicon Carbide<\/h2>\n<p>Use the structure described to predict the properties of a compound you have not met on this page.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-438\" class=\"h5p-iframe\" data-content-id=\"438\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Giant Covalent Structures MCQ: Silicon Carbide\"><\/iframe><\/div><\/div>\n<\/section>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Explain Silicon and Phosphorus<\/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-658\" class=\"h5p-iframe\" data-content-id=\"658\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Giant Covalent Structures Explain: Melting Temperatures of Silicon and White Phosphorus\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card purple\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">3<\/div>\n<h2>Graphite<\/h2>\n<\/div>\n<p>In <strong>graphite<\/strong> each carbon atom forms <strong>three covalent bonds<\/strong> to three other carbon atoms, giving flat <strong>hexagonal layers<\/strong> with bond angles of 120\u00b0. The fourth outer electron of each carbon is not used in a localised bond; it sits in a p orbital above and below the layer and becomes <strong>delocalised<\/strong> across the whole sheet. The layers are held to each other only by weak <strong>instantaneous dipole-induced dipole (id-id) forces<\/strong>, also called London dispersion forces, and are relatively far apart.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Property<\/th><th>Explanation from the structure<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Very high melting point<\/strong><\/td><td>The strong covalent bonds within the layers must be broken<\/td><\/tr>\n<tr><td><strong>Soft and slippery<\/strong><\/td><td>The weak forces between layers let them slide over each other; graphite is used as a lubricant and in pencils<\/td><\/tr>\n<tr><td><strong>Conducts electricity<\/strong><\/td><td>The delocalised electrons can move along the layers when a voltage is applied. Graphite conducts well along the layers but very poorly at right angles to them, because the electrons cannot move easily from one layer to the next<\/td><\/tr>\n<tr><td><strong>Low density compared with diamond<\/strong><\/td><td>The layers are widely spaced<\/td><\/tr>\n<tr><td><strong>Insoluble<\/strong><\/td><td>Covalent bonding throughout the layers<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n\n<div class=\"ols-key-box\">\n<p><strong>Exam focus:<\/strong> Graphite conducts because it has delocalised electrons; it is soft because the layers are held together only by weak id-id forces. Do not say the layers are held by covalent bonds, and do not say graphite conducts because it is a metal.<\/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: Which Way Does Graphite Conduct?<\/h2>\n<p>Predict what happens when the conductivity of a graphite crystal is measured in two directions.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-439\" class=\"h5p-iframe\" data-content-id=\"439\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Giant Covalent Structures MCQ: Conductivity of Graphite in Two Directions\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">4<\/div>\n<h2>Graphene<\/h2>\n<\/div>\n<p><strong>Graphene<\/strong> is a <strong>single layer of graphite<\/strong>: a sheet of carbon atoms one atom thick, each bonded covalently to three others in a hexagonal pattern, with one delocalised electron per carbon spread over the sheet. It is described as a two-dimensional giant covalent structure.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Property<\/th><th>Explanation<\/th><th>Application<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Extremely strong for its thickness<\/strong><\/td><td>Strong covalent bonds throughout the sheet<\/td><td>Reinforcing composites and lightweight materials<\/td><\/tr>\n<tr><td><strong>Excellent electrical conductor<\/strong><\/td><td>Delocalised electrons move freely across the sheet<\/td><td>Flexible electronics, touchscreens, sensors<\/td><\/tr>\n<tr><td><strong>Very good thermal conductor<\/strong><\/td><td>Vibrations pass easily through the rigid covalent network<\/td><td>Heat management in electronic devices<\/td><\/tr>\n<tr><td><strong>Transparent and flexible<\/strong><\/td><td>A single atomic layer absorbs little light and can bend without breaking bonds<\/td><td>Transparent conducting films<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n\n<div class=\"ols-key-box\">\n<p><strong>Exam sentence:<\/strong> Graphene is a single layer of graphite in which each carbon atom is covalently bonded to three others; the delocalised electrons make it an excellent conductor and the covalent network makes it very strong.<\/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: From Graphene to Nanotubes<\/h2>\n<p>Apply what you know about graphene to two related materials, answering each question as quickly as you can.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-659\" class=\"h5p-iframe\" data-content-id=\"659\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Giant Covalent Structures Quick Fire: From Graphene to Carbon Nanotubes\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">5<\/div>\n<h2>Comparing the Three Carbon Structures<\/h2>\n<\/div>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th><\/th><th>Diamond<\/th><th>Graphite<\/th><th>Graphene<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Bonds per carbon atom<\/strong><\/td><td>4<\/td><td>3<\/td><td>3<\/td><\/tr>\n<tr><td><strong>Arrangement<\/strong><\/td><td>Tetrahedral, 109.5\u00b0, three-dimensional<\/td><td>Hexagonal layers, 120\u00b0<\/td><td>One hexagonal layer, 120\u00b0<\/td><\/tr>\n<tr><td><strong>Delocalised electrons<\/strong><\/td><td>None<\/td><td>One per carbon, within each layer<\/td><td>One per carbon, across the sheet<\/td><\/tr>\n<tr><td><strong>Electrical conductivity<\/strong><\/td><td>None<\/td><td>Along the layers<\/td><td>Excellent<\/td><\/tr>\n<tr><td><strong>Hardness<\/strong><\/td><td>Extremely hard<\/td><td>Soft, layers slide<\/td><td>Very strong sheet<\/td><\/tr>\n<tr><td><strong>Melting point<\/strong><\/td><td>Very high<\/td><td>Very high<\/td><td>Very high<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> The same element gives three very different materials because the bonding arrangement differs: four localised bonds give hardness and no conduction; three bonds plus a delocalised electron give layers that conduct.<\/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: Two Forms of Boron Nitride<\/h2>\n<p>Drag the words into place to compare the two forms of another giant covalent substance.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-437\" class=\"h5p-iframe\" data-content-id=\"437\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Giant Covalent Structures Drag: Two Forms of Boron Nitride\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">6<\/div>\n<h2>Where This Sits in the Cambridge Syllabus<\/h2>\n<\/div>\n<p>Cambridge places giant molecular structures in <strong>4.2.1(c)<\/strong>: you must describe the lattice structures of <strong>silicon(IV) oxide, graphite and diamond<\/strong> in simple terms and use them to explain melting point and conductivity (4.2.2). <strong>Silicon(IV) oxide<\/strong>, SiO<sub>2<\/sub>, is a giant molecular structure in which each silicon atom is bonded tetrahedrally to four oxygen atoms and each oxygen bridges two silicon atoms, giving an extended Si-O network. It is very hard, has a high melting point (about 1700 \u00b0C), is insoluble in water and does not conduct, because every outer electron is used in Si-O bonds.<\/p>\n<!-- 3D card: giant-covalent-structures (26 Sep 2026) -->\n<section class=\"ols-gcs-001\" id=\"olsGcs001\">\n<style>\n@import url('https:\/\/fonts.googleapis.com\/css2?family=Poppins:wght@300;400;500;600&display=swap');\n\n.ols-gcs-001{\n  font-family:'Poppins',system-ui,-apple-system,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;\n  color:#1C244B; background:#ffffff;\n  border:1px solid rgba(28,36,75,0.14);\n  border-radius:28px;\n  box-shadow:0 18px 45px rgba(28,36,75,0.10);\n  padding:44px; margin:26px auto; max-width:980px;\n  box-sizing:border-box; -webkit-font-smoothing:antialiased;\n}\n.ols-gcs-001 *{box-sizing:border-box;}\n\n.ols-gcs-001 .gcs-head{margin:0 0 22px;}\n.ols-gcs-001 h2.gcs-title{\n  font-size:26px; line-height:1.25; font-weight:600; letter-spacing:-0.012em;\n  margin:0 0 9px; color:#1C244B;\n}\n.ols-gcs-001 p.gcs-sub{\n  font-size:14.5px; 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text-align:center; font-size:11px; font-style:italic; color:#aab0c0;\n}\n.ols-cc-gcs-001 a{color:#aab0c0; text-decoration:none;}\n.ols-cc-gcs-001 a:hover{text-decoration:underline;}\n<\/style>\n\n<div class=\"gcs-head\">\n  <h2 class=\"gcs-title\">Giant Covalent Structures: Diamond, Graphite, Graphene and SiO<sub>2<\/sub><\/h2>\n  <p class=\"gcs-sub\">Start from one atom and its bonds, build the network outwards, and see how the bonding in each structure explains its properties.<\/p>\n<\/div>\n\n<div class=\"gcs-stage\" id=\"gcsStage\">\n  <canvas class=\"gcs-canvas\" id=\"gcsCanvas\"><\/canvas>\n  <div class=\"gcs-overlay\" id=\"gcsOverlay\"><\/div>\n  <div class=\"gcs-caption\" id=\"gcsCaption\"><\/div>\n  <div class=\"gcs-hint\" id=\"gcsHint\">Drag to rotate<\/div>\n  <div class=\"gcs-badges\" id=\"gcsBadges\"><\/div>\n<\/div>\n\n<div class=\"gcs-controls\">\n  <div class=\"gcs-row\">\n    <span class=\"gcs-rowlab\">Structure<\/span>\n    <div class=\"gcs-seg\" role=\"group\" aria-label=\"Structure\">\n      <button type=\"button\" data-s=\"diamond\" aria-pressed=\"true\">Diamond<\/button>\n      <button type=\"button\" data-s=\"graphite\" aria-pressed=\"false\">Graphite<\/button>\n      <button type=\"button\" data-s=\"graphene\" aria-pressed=\"false\">Graphene<\/button>\n      <button type=\"button\" data-s=\"sio2\" aria-pressed=\"false\">Silicon(IV) oxide<\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"gcs-row\">\n    <span class=\"gcs-rowlab\">Step<\/span>\n    <div class=\"gcs-seg\" role=\"group\" aria-label=\"Step\">\n      <button type=\"button\" data-step=\"1\" aria-pressed=\"true\">One atom<\/button>\n      <button type=\"button\" data-step=\"2\" aria-pressed=\"false\">Network<\/button>\n      <button type=\"button\" data-step=\"3\" aria-pressed=\"false\">Properties<\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"gcs-row\">\n    <span class=\"gcs-rowlab\">View<\/span>\n    <div class=\"gcs-seg\" role=\"group\" aria-label=\"Camera view\">\n      <button type=\"button\" data-v=\"front\" aria-pressed=\"false\">Front<\/button>\n      <button type=\"button\" data-v=\"side\" aria-pressed=\"false\">Side<\/button>\n      <button type=\"button\" data-v=\"top\" aria-pressed=\"false\">Top<\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"gcs-row\">\n    <span class=\"gcs-rowlab\">Show<\/span>\n    <button type=\"button\" class=\"gcs-pill\" id=\"gcsTogLab\" aria-pressed=\"true\"><i class=\"dot\"><\/i>Labels<\/button>\n    <button type=\"button\" class=\"gcs-pill\" id=\"gcsTogBond\" aria-pressed=\"true\"><i class=\"dot\"><\/i>Bonds<\/button>\n    <button type=\"button\" class=\"gcs-pill p-red\" id=\"gcsTogDeloc\" aria-pressed=\"false\"><i class=\"dot\"><\/i>Delocalised electrons<\/button>\n    <button type=\"button\" class=\"gcs-pill\" id=\"gcsTogCell\" aria-pressed=\"false\"><i class=\"dot\"><\/i>Unit outline<\/button>\n    <button type=\"button\" class=\"gcs-pill\" id=\"gcsTogSlide\" aria-pressed=\"false\"><i class=\"dot\"><\/i>Slide layers<\/button>\n  <\/div>\n\n  <div class=\"gcs-row\">\n    <span class=\"gcs-rowlab\">Motion<\/span>\n    <button type=\"button\" class=\"gcs-pill\" id=\"gcsSpin\" aria-pressed=\"false\"><i class=\"dot\"><\/i>Rotation<\/button>\n    <button type=\"button\" class=\"gcs-pill\" id=\"gcsResetV\">Reset view<\/button>\n  <\/div>\n<\/div>\n\n<div class=\"gcs-info\">\n  <h3 id=\"gcsInfoTitle\"><\/h3>\n  <p id=\"gcsInfoText\"><\/p>\n  <div class=\"gcs-facts\" id=\"gcsFacts\"><\/div>\n  <div class=\"gcs-key\">\n    <span><i style=\"background:#484e5c; border-radius:50%\"><\/i>Carbon<\/span>\n    <span><i style=\"background:#c4a06e; border-radius:50%\"><\/i>Silicon<\/span>\n    <span><i style=\"background:#cd342c; border-radius:50%\"><\/i>Oxygen<\/span>\n    <span><i style=\"background:#b4b9c6\"><\/i>Covalent bond<\/span>\n    <span><i style=\"background:rgba(220,60,60,0.25)\"><\/i>Delocalised electrons<\/span>\n    <span><i style=\"background:#c9961c\"><\/i>Bond angle<\/span>\n    <span><i style=\"background:#ffffff; border:1.5px dashed rgba(28,36,75,0.6)\"><\/i>Unit outline<\/span>\n  <\/div>\n<\/div>\n<\/section>\n\n<p class=\"ols-cc-gcs-001\">&copy; Dr. Mohammed Al-Fatah &#8211; <a href=\"https:\/\/www.onlinelearningsystem.net\" target=\"_blank\" rel=\"noopener\">onlinelearningsystem.net<\/a><\/p>\n\n<script src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/JS\/giant-covalent-structures.js?v=20260926\"><\/script>\n<div class=\"ols-key-box\">\n<p><strong>Exam sentence:<\/strong> Silicon(IV) oxide has a giant molecular structure in which strong Si-O covalent bonds extend throughout the lattice, so it has a high melting point and does not conduct electricity.<\/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: Carbon Dioxide and Silicon(IV) Oxide<\/h2>\n<p>Explain why two oxides from the same group have such different melting points.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-660\" class=\"h5p-iframe\" data-content-id=\"660\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Giant Covalent Structures MCQ: Carbon Dioxide Compared with Silicon(IV) Oxide\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card purple\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">7<\/div>\n<h2>Common Exam Mistakes<\/h2>\n<\/div>\n<ul>\n<li>Saying graphite is soft because its covalent bonds are weak. The covalent bonds are strong; it is the forces between layers that are weak.<\/li>\n<li>Saying diamond conducts electricity, or that graphite conducts because it contains ions or is metallic. Only delocalised electrons explain the conduction.<\/li>\n<li>Describing melting as breaking intermolecular forces. In a giant covalent structure the covalent bonds themselves must be broken.<\/li>\n<li>Forgetting the bond angle: 109.5\u00b0 in diamond, 120\u00b0 in graphite and graphene.<\/li>\n<li>Drawing a diamond fragment with carbon atoms that have only three bonds, or a graphite layer with four bonds per carbon.<\/li>\n<\/ul>\n<div class=\"ols-key-box\">\n<p><strong>Exam sentence:<\/strong> Giant covalent structures have very high melting points because many strong covalent bonds must be broken; only those with delocalised electrons, graphite and graphene, conduct electricity.<\/p>\n<\/div>\n<\/article>\n\n<section class=\"ols-course-cta-covalent\" id=\"olsCourseCtaCovalent001\">\r\n  <style>\r\n    .ols-course-cta-covalent,\r\n    .ols-course-cta-covalent * {\r\n      box-sizing: border-box;\r\n    }\r\n\r\n    .ols-course-cta-covalent {\r\n      --navy: #1C244B;\r\n      --blue: #2563eb;\r\n      --body-text: #1f2937;\r\n      --grey-text: #667085;\r\n      --border: rgba(28, 36, 75, 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Shapes of Molecules interactive course banner\"\r\n          >\r\n        <\/div>\r\n\r\n      <\/a>\r\n\r\n      <div class=\"ols-course-cta-content\">\r\n\r\n        <div class=\"ols-course-cta-header-row\">\r\n\r\n          <div class=\"ols-course-cta-kicker\">\r\n            Cambridge 9701 | Topic 3 Course\r\n          <\/div>\r\n\r\n          <a class=\"ols-course-button ols-course-button-top\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/covalent-bonding-and-shapes-of-molecules-topic-3-cambridge-international\/\">\r\n            View Course\r\n          <\/a>\r\n\r\n        <\/div>\r\n\r\n        <h2>\r\n          Master Covalent Bonding and Shapes of Molecules for Cambridge International AS &amp; A Level Chemistry\r\n        <\/h2>\r\n\r\n      <\/div>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-cta-intro-stats\">\r\n\r\n      <p class=\"ols-course-cta-intro\">\r\n        Continue from these free revision notes into the full Topic 3 Covalent Bonding and Shapes of Molecules course. The guided video lessons are ready now; the Cambridge International MCQ bank, teacher-marked short-answer questions and KASP spec-point report are being written, and the course opens for enrolment as soon as they are complete.\r\n      <\/p>\r\n\r\n      <div class=\"ols-course-cta-stats\">\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>Recorded lessons<\/span>\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>Video lessons<\/span>\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>MCQ practice<\/span>\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>SAQ practice<\/span>\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n      <\/div>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-cta-features\">\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Guided video teaching<\/h3>\r\n        <p>\r\n          Learn the chemistry and exam technique through structured video lessons with worked examples and walkthroughs.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Instant MCQ feedback<\/h3>\r\n        <p>\r\n          Auto-marked MCQ quizzes provide immediate diagnostic feedback for every answer choice.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Teacher-marked SAQs<\/h3>\r\n        <p>\r\n          Submit written exam responses and receive chemistry specialist feedback with improvement guidance.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Progress tracking<\/h3>\r\n        <p>\r\n          Identify strengths and weaknesses across the full Topic 3 specification with targeted reporting.\r\n        <\/p>\r\n      <\/div>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-animation-wrap\">\r\n\r\n      <h3 class=\"ols-course-animation-title\">\r\n        See how the course works\r\n      <\/h3>\r\n\r\n      <div class=\"ols-animation-frame-shell\">\r\n        <iframe\r\n          id=\"olsCourseAnimationFrame001\"\r\n          title=\"OLS course preview animation\"\r\n          loading=\"lazy\"\r\n          referrerpolicy=\"no-referrer\">\r\n        <\/iframe>\r\n\r\n        <button\r\n          class=\"ols-animation-start-overlay\"\r\n          id=\"olsCourseAnimationStart001\"\r\n          type=\"button\"\r\n          aria-label=\"Play OLS course preview animation\">\r\n          <span class=\"ols-animation-start-content\">\r\n            <span class=\"ols-animation-play-circle\" aria-hidden=\"true\">\r\n              <span class=\"ols-animation-play-icon\"><\/span>\r\n            <\/span>\r\n            <span class=\"ols-animation-start-text\">\r\n              Play course preview animation\r\n            <\/span>\r\n          <\/span>\r\n        <\/button>\r\n\r\n        <button\r\n          class=\"ols-animation-pause-button\"\r\n          id=\"olsCourseAnimationPause001\"\r\n          type=\"button\"\r\n          aria-label=\"Pause course preview animation\">\r\n          Pause\r\n        <\/button>\r\n      <\/div>\r\n\r\n      <p class=\"ols-course-video-status\">\r\n        Click play to start the course preview animation.\r\n      <\/p>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-cta-bottom\">\r\n\r\n      <a class=\"ols-course-button\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/covalent-bonding-and-shapes-of-molecules-topic-3-cambridge-international\/\">\r\n        View Covalent Bonding and Shapes of Molecules 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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because it has more atoms packed together and melts at a higher temperature than sodium.\";\r\nconst saqTeacherFeedbackText=\r\n\"Comment:\\n\"+\r\n\"This answer is not correct. 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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Polar Molecules<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/ionic-bonding\/nature-of-ionic-bonding\/\">Nature of Ionic Bonding<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-3-chemical-bonding\/metallic-bonding\/metallic-bonding-and-structure\/\">Metallic Bonding and Structure<\/a>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-attribution-card\">\n        <p><strong>Copyright and author footprint:<\/strong> This OLS revision page was written for Online Learning System by <strong>Dr. Mohammed Al-Fatah<\/strong>. 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