{"id":4576,"date":"2026-05-30T06:09:20","date_gmt":"2026-05-30T05:09:20","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/structure-types\/"},"modified":"2026-10-25T14:00:15","modified_gmt":"2026-10-25T14:00:15","slug":"structure-types","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/structure-types\/","title":{"rendered":"Structure Types"},"content":{"rendered":"<script src=\"https:\/\/cdnjs.cloudflare.com\/ajax\/libs\/three.js\/r128\/three.min.js\"><\/script>\n\n<section class=\"ols-revision-page ols-nature-of-ionic-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      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.ols-table { border-collapse: separate; border-spacing: 0; }\n      .ols-table thead { display: none; }\n      .ols-table tr { margin-bottom: 14px; border: 1px solid var(--border); border-radius: 18px; overflow: hidden; background: #ffffff; box-shadow: var(--inner-shadow); }\n      .ols-table td { border-bottom: 1px solid var(--border); padding: 14px 16px; overflow-wrap: anywhere; }\n      .ols-table td:last-child { border-bottom: none; }\n      .ols-table td::before { content: attr(data-label); display: block; margin-bottom: 6px; font-size: 13px; font-weight: 700; color: var(--blue); }\n      .ols-author { align-items: flex-start; padding: 22px 18px; border-radius: 22px; }\n      .ols-author-avatar-img { width: 72px; height: 72px; }\n      .ols-author-title { font-size: 24px; }\n      .ols-author-description { font-size: 15px; }\n    }\n  \n    .ols-figure-placeholder .ols-placeholder-box { border: 2px dashed #c9973a; background: #fffaf0; border-radius: 16px; padding: 26px 22px; font-weight: 700; color: #7a4b12; text-align: center; line-height: 1.6; }\n    .ols-figure-placeholder .ols-figure-image { background: transparent; }\n    .ols-figure-placeholder { background: #ffffff; border: 1px solid rgba(28, 36, 75, 0.12); 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\">\r\n  <div class=\"ols-sidebar-header\">\r\n    <h3>Revision Notes<\/h3>\r\n    <p>A Level Chemistry<\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Topic 2 Bonding and Structure<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/ionic-bonding\/\">Ionic Bonding<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/ionic-bonding\/nature-of-ionic-bonding\/\">Nature of Ionic Bonding<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/ionic-bonding\/polarisation-of-ions\/\">Polarisation of Ions<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/ionic-bonding\/physical-properties-of-ionic-compounds\/\">Physical Properties of Ionic Compounds<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/covalent-bonding\/\">Covalent Bonding<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/covalent-bonding\/nature-of-covalent-bonding\/\">Nature of Covalent Bonding<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/covalent-bonding\/dative-covalent-bonding\/\">Dative Covalent Bonding<\/a>\r\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/covalent-bonding\/giant-covalent-structures\/\">Giant Covalent Structures<\/a>\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/covalent-bonding\/electronegativity\/\">Electronegativity<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/shapes-of-molecules\/\">Shapes of Molecules<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/shapes-of-molecules\/linear\/\">Linear<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/shapes-of-molecules\/trigonal-planar\/\">Trigonal Planar<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/shapes-of-molecules\/tetrahedral\/\">Tetrahedral<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/shapes-of-molecules\/trigonal-pyramidal\/\">Trigonal Pyramidal<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/shapes-of-molecules\/bent\/\">Bent<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/shapes-of-molecules\/trigonal-bipyramidal\/\">Trigonal Bipyramidal<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/shapes-of-molecules\/octahedral\/\">Octahedral<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/shapes-of-molecules\/square-planar\/\">Square Planar<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/shapes-of-molecules\/square-pyramidal\/\">Square Pyramidal<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/shapes-of-molecules\/distorted-t\/\">Distorted T<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/shapes-of-molecules\/seesaw\/\">SeeSaw<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/polar-molecules\/\">Polar Molecules<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/metallic-bonding\/\">Metallic Bonding<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/metallic-bonding\/metallic-bonding-and-structure\/\">Metallic Bonding and Structure<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/metallic-bonding\/physical-properties-of-metals\/\">Physical Properties of Metals<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/intermolecular-forces\/\">Intermolecular Forces<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/intermolecular-forces\/london-forces\/\">London Forces<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/intermolecular-forces\/permanent-dipole-dipole-forces\/\">Permanent Dipole-Dipole Forces<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/intermolecular-forces\/hydrogen-bonding\/\">Hydrogen Bonding<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/intermolecular-forces\/anomalous-properties-of-water\/\">Anomalous Properties of Water<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/intermolecular-forces\/boiling-temperature-trends\/\">Boiling Temperature Trends<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/intermolecular-forces\/choosing-solvents\/\">Choosing Solvents<\/a>\n          <\/li>\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/structure-types\/\">Structure Types<\/a>\r\n      <\/li>\r\n\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Next Topics<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-3-redox-i\/\">Redox I<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/\">Inorganic Chemistry &amp; The Periodic Table<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-5-formulae-equations-and-amounts-of-substance\/\">Formulae, Equations &amp; Amounts<\/a>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n<\/aside>\r\n\r\n<script>\r\n(function() {\r\n  function normalisePath(path) {\r\n    return String(path || '')\r\n      .split('?')[0]\r\n      .split('#')[0]\r\n      .replace(\/\\\/+$\/, '')\r\n      .toLowerCase();\r\n  }\r\n\r\n  function highlightActive() {\r\n    var sidebar = document.querySelector('.ols-sidebar');\r\n    if (!sidebar) return false;\r\n\r\n    var currentPath = normalisePath(window.location.pathname);\r\n    var links = sidebar.querySelectorAll('a[href]');\r\n    var matched = null;\r\n    var matchedLength = 0;\r\n\r\n    sidebar.querySelectorAll('.active, .active-main, .parent-active').forEach(function(item) {\r\n      item.classList.remove('active', 'active-main', 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lattice, giant ionic, giant metallic, giant covalent and simple molecular: which particles they contain, what holds them together, and how that decides melting temperature, conductivity, solubility and the energy changes on melting and boiling.<\/p>\n\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Unit: Paper 1<\/div>\n          <div class=\"ols-badge\">Topic 2: Bonding and Structure<\/div>\n          <div class=\"ols-badge\">9CH0\/01<\/div>\n        <\/div>\n      <\/header>\n<!-- Copyright (c) 2026 Dr. Mohammed Al-Fatah, onlinelearningsystem.net. 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align-items:center; justify-content:center; width:20px; height:20px; margin-right:9px; border-radius:50%; font-size:11px; font-weight:600; background:rgba(37,99,235,0.10); color:#2563eb; flex:0 0 auto;}\n.ols-slds-001 .slds-seg button[aria-pressed=\"true\"] .slds-n{background:#ffffff; color:#2563eb;}\n<\/style>\n\n<div class=\"slds-head\">\n  <h2 class=\"slds-title\">The Four Types of Solid Lattice<\/h2>\n  <p class=\"slds-sub\">Choose a step to watch each type of solid lattice form, see what holds its particles together, then press Heat it to see what melting that solid has to overcome.<\/p>\n<\/div>\n\n<div class=\"slds-stage\" id=\"sldsStage\">\n  <canvas class=\"slds-canvas\" id=\"sldsCanvas\"><\/canvas>\n  <div class=\"slds-overlay\" id=\"sldsOverlay\"><\/div>\n  <div class=\"slds-caption\" id=\"sldsCaption\"><\/div>\n  <div class=\"slds-hint\" id=\"sldsHint\">Drag to rotate<\/div>\n  <div class=\"slds-badges\" id=\"sldsBadges\"><\/div>\n<\/div>\n\n<div class=\"slds-controls\">\n  <div class=\"slds-row\">\n    <span class=\"slds-rowlab\">Step<\/span>\n    <div class=\"slds-seg\" role=\"group\" aria-label=\"Step\">\n      <button type=\"button\" data-step=\"1\" aria-pressed=\"true\"><span class=\"slds-n\">1<\/span>Giant ionic<\/button>\n      <button type=\"button\" data-step=\"2\" aria-pressed=\"false\"><span class=\"slds-n\">2<\/span>Giant metallic<\/button>\n      <button type=\"button\" data-step=\"3\" aria-pressed=\"false\"><span class=\"slds-n\">3<\/span>Giant covalent<\/button>\n      <button type=\"button\" data-step=\"4\" aria-pressed=\"false\"><span class=\"slds-n\">4<\/span>Simple molecular<\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"slds-row\">\n    <span class=\"slds-rowlab\">View<\/span>\n    <button type=\"button\" class=\"slds-pill slds-heat\" id=\"sldsHeat\" aria-pressed=\"false\"><svg viewBox=\"0 0 16 16\" aria-hidden=\"true\"><path fill=\"currentColor\" d=\"M8.6 1c.3 2.3-1.1 3.4-2.2 4.8C5.3 7.1 4.5 8.4 4.5 10a3.5 3.5 0 0 0 7 0c0-1.5-.7-2.6-1.4-3.4.1 1.1-.3 2-1 2.4.3-2.6-.2-5.6-.5-8z\"\/><\/svg><span id=\"sldsHeatLab\">Heat it<\/span><\/button>\n    <button type=\"button\" class=\"slds-pill\" id=\"sldsResetV\">Reset view<\/button>\n  <\/div>\n<\/div>\n\n<div class=\"slds-info\">\n  <h3 id=\"sldsInfoTitle\"><\/h3>\n  <p id=\"sldsInfoText\"><\/p>\n  <div class=\"slds-facts\" id=\"sldsFacts\"><\/div>\n  <div class=\"slds-key\">\n    <span><i class=\"k-ball\" style=\"background:#8c52c4\"><\/i>Sodium ion, Na\u207a<\/span>\n    <span><i class=\"k-ball\" style=\"background:#34aa48\"><\/i>Chloride ion, Cl\u207b<\/span>\n    <span><i class=\"k-ball\" style=\"background:#b2b8c4\"><\/i>Magnesium ion, Mg\u00b2\u207a<\/span>\n    <span><i class=\"k-ball\" style=\"background:#f2bc1a\"><\/i>Delocalised electron<\/span>\n    <span><i class=\"k-ball\" style=\"background:#464a54\"><\/i>Carbon atom<\/span>\n    <span><i class=\"k-ball\" style=\"background:#682c8c\"><\/i>Iodine atom<\/span>\n    <span><i class=\"\" style=\"background:#ffffff;border-color:rgba(201,150,28,0.95)\"><\/i>Electrostatic attraction<\/span>\n    <span><i class=\"\" style=\"background:#ffffff;border-color:rgba(70,125,190,0.85)\"><\/i>London forces<\/span>\n  <\/div>\n<\/div>\n\n<script src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/JS\/solid-lattices.js?v=20261025i\"><\/script>\n<\/section>\n\n<p class=\"ols-cc-slds-001\">&copy; Dr. Mohammed Al-Fatah &#8211; <a href=\"https:\/\/www.onlinelearningsystem.net\" target=\"_blank\" rel=\"noopener\">onlinelearningsystem.net<\/a><\/p>\n\n\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: Bonding Types and Changes of State<\/h2>\n<p>Answer three quick GCSE questions before you start.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"690\"><\/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>The Four Types of Solid Lattice<\/h2>\n<\/div>\n<p>Every crystalline solid is a regular, repeating arrangement of particles: a <strong>lattice<\/strong>. What decides a solid&#8217;s properties is not the lattice pattern itself but <strong>which particles<\/strong> sit at the lattice points and <strong>which forces<\/strong> hold them there. There are four cases to know.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Lattice type<\/th><th>Particles<\/th><th>Forces holding the lattice together<\/th><th>Examples<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Giant ionic<\/strong><\/td><td>Positive and negative ions<\/td><td>Strong electrostatic attraction between oppositely charged ions, acting in all directions<\/td><td>NaCl, MgO, CaF<sub>2<\/sub><\/td><\/tr>\n<tr><td><strong>Giant metallic<\/strong><\/td><td>Positive metal ions and delocalised electrons<\/td><td>Strong electrostatic attraction between the ions and the sea of delocalised electrons<\/td><td>Mg, Cu, Na<\/td><\/tr>\n<tr><td><strong>Giant covalent (macromolecular)<\/strong><\/td><td>Atoms<\/td><td>Strong covalent bonds throughout the whole structure<\/td><td>Diamond, graphite, SiO<sub>2<\/sub><\/td><\/tr>\n<tr><td><strong>Simple molecular<\/strong><\/td><td>Molecules<\/td><td>Weak intermolecular forces between molecules (the covalent bonds inside each molecule are strong but are not broken on melting)<\/td><td>I<sub>2<\/sub>, ice, C<sub>60<\/sub>, CO<sub>2<\/sub><\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>The word <strong>giant<\/strong> means the bonding continues throughout the crystal, so there is no separate molecule to point to.<\/p>\n<p>In a <strong>simple molecular<\/strong> solid there are two different forces: strong covalent bonds within each molecule and weak forces between them, and only the weak forces are overcome when the solid melts.<\/p>\n\n\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> Three giant lattices, one molecular lattice. Melting a giant lattice breaks strong bonds; melting a molecular lattice only overcomes weak intermolecular forces.<\/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: Spot the Molecular Solids<\/h2>\n<p>Click every substance that would form a simple molecular lattice.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-691\" class=\"h5p-iframe\" data-content-id=\"691\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Structure Types Mark the Words: Which Solids Are Simple Molecular?\"><\/iframe><\/div><\/div>\n<\/section>\n\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">2<\/div>\n<h2>Melting Temperature Follows the Force That Must Be Overcome<\/h2>\n<\/div>\n<p>Melting a solid means giving the particles enough energy to break free from their lattice positions. The energy needed depends on the force holding them, so melting temperatures fall into two clear bands.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Substance<\/th><th>Lattice type<\/th><th>What must be overcome on melting<\/th><th>Melting temperature \/ \u00b0C<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Sodium chloride<\/strong><\/td><td>Giant ionic<\/td><td>Strong electrostatic attraction between ions<\/td><td>801<\/td><\/tr>\n<tr><td><strong>Magnesium<\/strong><\/td><td>Giant metallic<\/td><td>Strong attraction between ions and delocalised electrons<\/td><td>650<\/td><\/tr>\n<tr><td><strong>Diamond<\/strong><\/td><td>Giant covalent<\/td><td>Strong covalent bonds<\/td><td>above 3500 (sublimes)<\/td><\/tr>\n<tr><td><strong>Iodine<\/strong><\/td><td>Simple molecular<\/td><td>Weak London forces between I<sub>2<\/sub> molecules<\/td><td>114<\/td><\/tr>\n<tr><td><strong>Ice<\/strong><\/td><td>Simple molecular<\/td><td>Hydrogen bonds between H<sub>2<\/sub>O molecules<\/td><td>0<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>Within a band the details matter.<\/p><div class=\"ols-table-wrap\"><table class=\"ols-table\"><thead><tr><th>Type<\/th><th>What gives a higher melting temperature<\/th><\/tr><\/thead><tbody><tr><td><strong>Ionic compounds<\/strong><\/td><td>A higher charge and a smaller ionic radius give stronger attraction and a higher melting temperature (MgO melts at 2852 \u00b0C, NaCl at 801 \u00b0C)<\/td><\/tr><tr><td><strong>Metals<\/strong><\/td><td>More delocalised electrons per ion and a smaller ion give a higher melting temperature (Mg above Na)<\/td><\/tr><\/tbody><\/table><\/div><p>Among simple molecular substances two things decide the melting temperature. <strong>For molecules of similar size<\/strong>, that is with similar numbers of electrons, the order is hydrogen bonds above permanent dipoles above London forces.<\/p><p>Size matters as well, because a larger molecule has more electrons and therefore stronger London forces.<\/p><p>That is why iodine, with only London forces, melts at 114 \u00b0C, well above ice at 0 \u00b0C, although ice has hydrogen bonds: an I<sub>2<\/sub> molecule is far larger than an H<sub>2<\/sub>O molecule.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Exam sentence:<\/strong> Sodium chloride has a high melting temperature because a lot of energy is needed to overcome the strong electrostatic attraction between oppositely charged ions in the giant lattice.<\/p>\n<p>Iodine has a low melting temperature because only weak London forces between I<sub>2<\/sub> molecules need to be overcome.<\/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: Explain Two Melting Points<\/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-461\" class=\"h5p-iframe\" data-content-id=\"461\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Structure Types Explain: Magnesium Chloride and Silicon Tetrachloride\"><\/iframe><\/div><\/div>\n<\/section>\n\n<article class=\"ols-note-card purple\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">3<\/div>\n<h2>Electrical Conductivity Needs Mobile Charged Particles<\/h2>\n<\/div>\n<p>A substance conducts electricity only if it contains <strong>charged particles that are free to move<\/strong>. Apply that one test to each lattice type in each state.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Lattice type<\/th><th>Solid<\/th><th>Molten or dissolved<\/th><th>Reason<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Giant ionic<\/strong><\/td><td>Does not conduct<\/td><td>Conducts<\/td><td>Ions are fixed in the solid lattice; when molten or in solution they are free to move and carry charge<\/td><\/tr>\n<tr><td><strong>Giant metallic<\/strong><\/td><td>Conducts<\/td><td>Conducts<\/td><td>Delocalised electrons are free to move through the lattice in both states<\/td><\/tr>\n<tr><td><strong>Giant covalent<\/strong><\/td><td>Does not conduct (except graphite)<\/td><td>Does not conduct<\/td><td>All outer electrons are held in localised covalent bonds; graphite alone has one delocalised electron per carbon<\/td><\/tr>\n<tr><td><strong>Simple molecular<\/strong><\/td><td>Does not conduct<\/td><td>Does not conduct<\/td><td>Molecules are neutral and there are no delocalised electrons or ions<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>The ionic case is the one examiners test most: the solid is an insulator, the melt is a conductor, and the reason is the <strong>mobility<\/strong> of the ions, not whether ions exist.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Exam focus:<\/strong> Never write &#8220;ionic compounds conduct electricity&#8221;. Write &#8220;ionic compounds conduct when molten or aqueous because the ions are free to move; in the solid the ions are held in fixed positions&#8221;.<\/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: When Does Potassium Bromide Conduct?<\/h2>\n<p>Use the data to choose the structure and the reason for the conductivity.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-460\" class=\"h5p-iframe\" data-content-id=\"460\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Structure Types MCQ: Potassium Bromide\"><\/iframe><\/div><\/div>\n<\/section>\n\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">4<\/div>\n<h2>Solubility and Hardness<\/h2>\n<\/div>\n<ul>\n<li><strong>Giant ionic:<\/strong> many dissolve in water because the polar water molecules attract the ions and hydrate them; insoluble in non-polar solvents. Hard but brittle, because shifting a layer brings like charges together and the layers repel.<\/li>\n<li><strong>Giant metallic:<\/strong> insoluble in all common solvents; malleable and ductile because layers of ions slide past each other while the electron sea keeps the attraction.<\/li>\n<li><strong>Giant covalent:<\/strong> insoluble in everything; very hard (diamond) or soft and slippery (graphite, where layers slide).<\/li>\n<li><strong>Simple molecular:<\/strong> soft, easily crushed; solubility follows polarity (&#8220;like dissolves like&#8221;): iodine dissolves in hexane, not in water; sugar and ethanol dissolve in water because they can hydrogen bond with it.<\/li>\n<\/ul>\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> Solubility is about the forces between solute and solvent; hardness is about how easily the lattice can be deformed without the forces breaking.<\/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: Shatter, Bend or Dissolve<\/h2>\n<p>Drag the words into place to explain three test results.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-692\" class=\"h5p-iframe\" data-content-id=\"692\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Structure Types Drag: Shattering, Bending and Dissolving\"><\/iframe><\/div><\/div>\n<\/section>\n\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">5<\/div>\n<h2>Energy Changes on Changes of State<\/h2>\n<\/div>\n<p>When a solid melts or a liquid boils, energy is absorbed to overcome the forces between particles while the temperature stays constant: the <strong>enthalpy of fusion<\/strong> and <strong>enthalpy of vaporisation<\/strong>. The size of each depends on the lattice type.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Change<\/th><th>Giant lattices<\/th><th>Simple molecular<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Melting<\/strong><\/td><td>Large energy input: strong ionic, metallic or covalent bonds are partly broken<\/td><td>Small energy input: some weak intermolecular forces are overcome<\/td><\/tr>\n<tr><td><strong>Boiling<\/strong><\/td><td>Very large: the remaining strong bonds are broken so the particles separate completely<\/td><td>Small: all the remaining intermolecular forces are overcome; the covalent bonds inside the molecules survive<\/td><\/tr>\n<tr><td><strong>Sign of the enthalpy change<\/strong><\/td><td>Endothermic (positive)<\/td><td>Endothermic (positive)<\/td><\/tr>\n<tr><td><strong>Reverse change (freezing, condensing)<\/strong><\/td><td>Exothermic: the same amount of energy is released as the forces re-form<\/td><td>Exothermic<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>On a heating curve the two flat plateaus are melting and boiling: the energy supplied is going into overcoming forces, not into raising the temperature. The plateaus are longer and sit at higher temperatures for giant lattices than for simple molecular substances.<\/p>\n<div class=\"ols-zoom-card\">\n<div class=\"ols-zoom-card-image\">\n<a class=\"ols-lightbox-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/wave-15.jpg\" aria-label=\"Open image full screen\">\n<img decoding=\"async\" class=\"ols-zoomable-img ols-lightbox-target\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/wave-15.jpg\" alt=\"Heating curves of a named giant ionic solid and a named simple molecular solid on one set of axes, with what is overcome at each plateau\">\n<\/a>\n<\/div>\n<div class=\"ols-zoom-card-caption\"><p>Energy supplied during a plateau overcomes forces between particles; the temperature does not rise until they are overcome.<\/p><\/div>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Exam sentence:<\/strong> During melting the temperature stays constant because the energy supplied is used to overcome the forces between the particles rather than to increase their kinetic energy.<\/p>\n<\/div>\n<\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: The Plateau for Sulfur<\/h2>\n<p>Decide where the energy goes while the temperature stays constant.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-462\" class=\"h5p-iframe\" data-content-id=\"462\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Structure Types MCQ: The Heating Curve Plateau\"><\/iframe><\/div><\/div>\n<\/section>\n\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">6<\/div>\n<h2>Deducing the Structure from Data<\/h2>\n<\/div>\n<p>Exam questions often give a table of properties for unnamed substances and ask for the structure and bonding. Work through the tests in order.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Question to ask<\/th><th>If yes<\/th><th>If no<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Does it conduct as a solid?<\/strong><\/td><td>Metallic (or graphite)<\/td><td>Go on<\/td><\/tr>\n<tr><td><strong>Does it conduct when molten but not as a solid?<\/strong><\/td><td>Giant ionic<\/td><td>Go on<\/td><\/tr>\n<tr><td><strong>Is the melting temperature very high (above about 1000 \u00b0C) with no conduction in any state?<\/strong><\/td><td>Giant covalent<\/td><td>Go on<\/td><\/tr>\n<tr><td><strong>Is the melting temperature low and there is no conduction?<\/strong><\/td><td>Simple molecular<\/td><td>Re-check the data<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>Then confirm with solubility: ionic solids often dissolve in water, molecular solids dissolve in solvents of similar polarity, giant covalent and metallic solids dissolve in neither.<\/p>\n<p>Keep to that order. Plenty of ionic solids also melt far above 1000 \u00b0C, MgO at 2852 \u00b0C, so a high melting temperature <strong>on its own<\/strong> does not prove giant covalent. It is the conduction test, done first, that separates the two.<\/p>\n<p>One warning about data tables. A few simple molecular substances <strong>react with water to form ions<\/strong>, so their solutions conduct although the pure substance does not.<\/p>\n<p>Hydrogen chloride is the example: it is a molecular gas, but hydrochloric acid conducts. A low melting temperature with conduction only in aqueous solution points to this, not to a giant ionic lattice.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Exam focus:<\/strong> State the structure, then justify it with two properties from the data, naming the particles and the forces each time.<\/p>\n<\/div>\n<div class=\"ols-zoom-card\">\n<div class=\"ols-zoom-card-image\">\n<a class=\"ols-lightbox-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t3-img-13-structurefromdata.jpg\" aria-label=\"Open image full screen\">\n<img decoding=\"async\" class=\"ols-zoomable-img ols-lightbox-target\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t3-img-13-structurefromdata.jpg\" alt=\"Flowchart from conductivity and melting data to giant metallic, giant ionic, giant covalent or simple molecular, with warning notes\">\n<\/a>\n<\/div>\n<div class=\"ols-zoom-card-caption\"><p>Test conductivity first, then melting behaviour, to decide between metallic, ionic, giant covalent and simple molecular.<\/p><\/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: Six Unknown Solids<\/h2>\n<p>Read each set of data and pick the structure as quickly as you can.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-459\" class=\"h5p-iframe\" data-content-id=\"459\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Structure Types Quick Fire: Deduce the Structure from the Data\"><\/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: The Whole Page in Six Rounds<\/h2>\n<p>Pick the one accurate statement in each round to pull the four lattice types together.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-1313\" class=\"h5p-iframe\" data-content-id=\"1313\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Structure Types Summary: Particles, Forces and Properties Across All Four Lattices\"><\/iframe><\/div><\/div>\n<\/section>\n\n<article class=\"ols-note-card soft\">\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 a simple molecular solid melts when &#8220;the covalent bonds break&#8221;. Only the intermolecular forces are overcome; the molecules stay intact.<\/li>\n<li>Saying ionic compounds conduct electricity without stating the condition (molten or aqueous) and the reason (ions free to move).<\/li>\n<li>Calling the attraction in a metal &#8220;between atoms&#8221; or &#8220;between ions&#8221;. It is between positive ions and delocalised electrons.<\/li>\n<li>Describing diamond as a molecule. It is a giant covalent lattice with no separate molecules.<\/li>\n<li>Explaining a high melting temperature by &#8220;strong bonds&#8221; alone. Name the type of bond or force and the particles it acts between.<\/li>\n<\/ul>\n<div class=\"ols-key-box\">\n<p><strong>Exam sentence:<\/strong> Particles, force between them, consequence: every structure-and-bonding answer follows that pattern.<\/p>\n<\/div>\n<\/article>\n<article class=\"ols-note-card purple\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">8<\/div>\n<h2>Where This Sits in the Edexcel Specification<\/h2>\n<\/div>\n<p>Edexcel Topic 2 expects you to describe ionic, metallic and covalent structures separately and then to use them together to explain physical properties.<\/p>\n<p>This page brings the four lattice types side by side so that a question giving melting temperature and conductivity data can be answered by working from the data to the structure.<\/p><div class=\"ols-key-box\">\n<p><strong>Exam focus:<\/strong> A giant lattice needs strong bonds broken to melt it; a simple molecular lattice needs only weak intermolecular forces overcome. Say which, and name the particles.<\/p>\n<\/div>\n<\/article>\n\n<section class=\"ols-faq-card\">\n<h2>FAQs<\/h2>\n<p>These questions cover the structure-type mistakes that cost marks most often.<\/p>\n<div class=\"ols-faq-list\">\n<div class=\"ols-faq-item\">\n<h3>Why does iodine melt above ice if hydrogen bonds are stronger than London forces?<\/h3>\n<p>Hydrogen bonds are stronger only for molecules of similar size. An I<sub>2<\/sub> molecule has 106 electrons against 10 in H<sub>2<\/sub>O, so its London forces add up to more. Iodine melts at 114 \u00b0C, ice at 0 \u00b0C.<\/p>\n<\/div>\n<div class=\"ols-faq-item\">\n<h3>Do covalent bonds break when a simple molecular solid melts?<\/h3>\n<p>No. Only the intermolecular forces between the molecules are overcome. The covalent bonds inside each molecule stay intact, which is why iodine vapour still contains I<sub>2<\/sub> molecules.<\/p>\n<\/div>\n<div class=\"ols-faq-item\">\n<h3>Why does solid sodium chloride not conduct when it contains ions?<\/h3>\n<p>The ions are fixed in the lattice and cannot move. Sodium chloride conducts only when molten or dissolved in water, because the ions are then free to move and carry charge.<\/p>\n<\/div>\n<div class=\"ols-faq-item\">\n<h3>How can I tell a giant covalent solid from an ionic one using data?<\/h3>\n<p>Both have very high melting temperatures, so check conductivity. An ionic solid conducts when molten or in aqueous solution. A giant covalent solid such as diamond or silicon dioxide conducts in no state; graphite is the exception.<\/p>\n<\/div>\n<div class=\"ols-faq-item\">\n<h3>Why does a solution of hydrogen chloride conduct if HCl is a simple molecule?<\/h3>\n<p>Hydrogen chloride reacts with water to form H<sup>+<\/sup>(aq) and Cl<sup>&#8211;<\/sup>(aq) ions. The pure substance is molecular and does not conduct; the ions only appear in solution.<\/p>\n<\/div>\n<\/div>\n<\/section>\n\n      <!-- author card (moved to the end, 10 Oct 2026) -->\n      <div class=\"ols-author\">\n\n    <img decoding=\"async\"\n      class=\"ols-author-avatar-img\"\n      src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\"\n      alt=\"Dr. Mohammed Al-Fatah\"\n    >\n\n    <div class=\"ols-author-content\">\n\n      <h2 class=\"ols-author-title\">\n        Written by: Dr. Mohammed Al-Fatah\n      <\/h2>\n\n      <p class=\"ols-author-description\">\n        Chemistry specialist revision notes for A Level Chemistry.\n      <\/p>\n\n      <a\n        class=\"ols-linkedin-pill\"\n        href=\"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\"\n        target=\"_blank\"\n        rel=\"noopener noreferrer\"\n      >\n\n        <svg class=\"ols-linkedin-icon\" viewBox=\"0 0 24 24\" fill=\"currentColor\" aria-hidden=\"true\">\n          <path d=\"M4.98 3.5C4.98 4.88 3.86 6 2.48 6S0 4.88 0 3.5 1.12 1 2.48 1s2.5 1.12 2.5 2.5zM.5 8h4V24h-4V8zm7 0h3.8v2.2h.1c.5-.9 1.8-2.2 3.9-2.2 4.2 0 5 2.8 5 6.4V24h-4v-7.6c0-1.8 0-4.2-2.6-4.2s-3 2-3 4v7.8h-4V8z\"\/>\n        <\/svg>\n\n        View LinkedIn Profile\n\n      <\/a>\n\n    <\/div>\n\n  <\/div>\n\n\n<section class=\"ols-related-card\">\n        <h2>Related Bonding &amp; Structure Revision Notes<\/h2>\n        <p>Continue through Topic 2 by linking ionic bonding to polarisation, ionic properties and covalent bonding.<\/p>\n\n        <div class=\"ols-related-grid\">\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/ionic-bonding\/polarisation-of-ions\/\">Polarisation of Ions<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/ionic-bonding\/physical-properties-of-ionic-compounds\/\">Physical Properties of Ionic Compounds<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/covalent-bonding\/\">Covalent Bonding<\/a>\n        <\/div>\n      <\/section>\n\n    \n\n      <section class=\"ols-attribution-card ols-attr-std\" aria-label=\"Copyright notice\">\n<style id=\"ols-attribution-card-css\">.ols-attribution-card.ols-attr-std{background:linear-gradient(135deg,#ffffff,#f8fbff);border:1px solid rgba(28,36,75,0.14);border-radius:28px;box-shadow:0 18px 45px rgba(28,36,75,0.10);padding:34px;margin:24px 0;overflow:hidden;font-family:Poppins,Arial,sans-serif;box-sizing:border-box}.ols-attribution-card.ols-attr-std *{box-sizing:border-box}.ols-attribution-card.ols-attr-std p{margin:0;font-size:14px;line-height:1.65;font-weight:300;color:#667085}.ols-attribution-card.ols-attr-std strong{font-weight:700;color:#1C244B}@media (max-width:760px){.ols-attribution-card.ols-attr-std{padding:24px 18px;border-radius:22px}}<\/style>\n<p><strong>Copyright notice:<\/strong> This OLS revision content, including the explanations, layout, diagrams, tables and embedded learning structure, is authored for Online Learning System by Dr. Mohammed Al-Fatah. It may not be copied, reproduced, redistributed or adapted without written permission.<\/p>\n<\/section>\n      <div class=\"ols-image-lightbox\" role=\"dialog\" aria-modal=\"true\" aria-label=\"Image lightbox\">\n        <div class=\"ols-image-lightbox-inner\">\n          <button class=\"ols-image-lightbox-close\" type=\"button\" aria-label=\"Close image lightbox\">&times;<\/button>\n          <img decoding=\"async\" class=\"ols-image-lightbox-img\" src=\"\" alt=\"\">\n        <\/div>\n      <\/div>\n    <\/main>\n<script>\n(function(){\n  var wrap = document.querySelector('.ols-nature-of-ionic-bonding-9ch0-page');\n  if (!wrap) return;\n\n  var targets = wrap.querySelectorAll('.ols-lightbox-target');\n  var overlay = wrap.querySelector('.ols-image-lightbox');\n  var lbImg = wrap.querySelector('.ols-image-lightbox-img');\n  var closeBtn = wrap.querySelector('.ols-image-lightbox-close');\n\n  if (!overlay || !lbImg || !closeBtn || !targets.length) return;\n\n  targets.forEach(function(img){\n    img.addEventListener('click', function(){\n      lbImg.src = img.src;\n      lbImg.alt = img.alt || '';\n      overlay.classList.add('is-open');\n      document.body.style.overflow = 'hidden';\n    });\n  });\n\n  function closeLightbox(){\n    overlay.classList.remove('is-open');\n    document.body.style.overflow = '';\n    lbImg.src = '';\n    lbImg.alt = '';\n  }\n\n  closeBtn.addEventListener('click', closeLightbox);\n  overlay.addEventListener('click', function(event){\n    if (event.target === overlay) {\n      closeLightbox();\n    }\n  });\n  document.addEventListener('keydown', function(event){\n    if (event.key === 'Escape' && overlay.classList.contains('is-open')) {\n      closeLightbox();\n    }\n  });\n})();\n<\/script>\n<script type=\"application\/ld+json\">\n{\n    \"@context\": \"https:\/\/schema.org\",\n    \"@graph\": [\n        {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/structure-types\/#webpage\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-2-bonding-and-structure\/structure-types\/\",\n            \"name\": \"Structure Types - 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