{"id":5386,"date":"2026-06-24T09:25:50","date_gmt":"2026-06-24T08:25:50","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/hydrogen-bonding-2\/"},"modified":"2026-09-18T11:29:58","modified_gmt":"2026-09-18T10:29:58","slug":"hydrogen-bonding","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/hydrogen-bonding\/","title":{"rendered":"Hydrogen Bonding"},"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-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  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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>AQA A Level Chemistry<\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>3.1.3 Bonding<\/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\/aqa\/3-1-3-bonding\/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\/aqa\/3-1-3-bonding\/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\/aqa\/3-1-3-bonding\/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\/aqa\/3-1-3-bonding\/ionic-bonding\/physical-properties-of-ionic-compounds\/\">Physical Properties of Ionic Compounds<\/a>\r\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/ionic-bonding\/ions-and-ionic-formulae\/\">Ions and Ionic Formulae<\/a>\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\/aqa\/3-1-3-bonding\/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\/aqa\/3-1-3-bonding\/covalent-bonding\/covalent-bonding\/\">Covalent Bonding<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/covalent-bonding\/dative-covalent-bonding\/\">Dative Covalent Bonding<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/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\/aqa\/3-1-3-bonding\/shapes-of-molecules-and-ions\/\">Shapes of Molecules and Ions<\/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\/aqa\/3-1-3-bonding\/shapes-of-molecules-and-ions\/linear\/\">Linear<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/shapes-of-molecules-and-ions\/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\/aqa\/3-1-3-bonding\/shapes-of-molecules-and-ions\/tetrahedral\/\">Tetrahedral<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/shapes-of-molecules-and-ions\/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\/aqa\/3-1-3-bonding\/shapes-of-molecules-and-ions\/bent\/\">Bent<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/shapes-of-molecules-and-ions\/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\/aqa\/3-1-3-bonding\/shapes-of-molecules-and-ions\/octahedral\/\">Octahedral<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/shapes-of-molecules-and-ions\/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\/aqa\/3-1-3-bonding\/shapes-of-molecules-and-ions\/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\/aqa\/3-1-3-bonding\/shapes-of-molecules-and-ions\/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\/aqa\/3-1-3-bonding\/shapes-of-molecules-and-ions\/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\/aqa\/3-1-3-bonding\/bond-polarity\/\">Bond Polarity<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/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\/aqa\/3-1-3-bonding\/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\/aqa\/3-1-3-bonding\/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\/aqa\/3-1-3-bonding\/giant-covalent-structures\/\">Giant Covalent Structures<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/simple-molecular-structures\/\">Simple Molecular Structures<\/a>\r\n      <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/structure-types\/\">Structure Types<\/a>\n          <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/\">Intermolecular Forces<\/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\/aqa\/3-1-3-bonding\/intermolecular-forces\/london-forces\/\">London Forces<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/permanent-dipole-dipole-forces\/\">Permanent Dipole-Dipole Forces<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/hydrogen-bonding\/\">Hydrogen Bonding<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/anomalous-properties-of-water\/\">Anomalous Properties of Water<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/boiling-temperature-trends\/\">Boiling Point Trends<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/choosing-solvents\/\">Choosing Solvents<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Adjacent 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\/aqa\/3-1-1-atomicstructure\/\">3.1.1 Atomic Structure<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/\">3.1.2 Amount of Substance<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-4-energetics\/\">3.1.4 Energetics<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-2-1-periodicity\/\">3.2.1 Periodicity<\/a>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n<\/aside>\r\n\r\n<script>\r\n(function() {\r\n  function normalisePath(path) {\r\n    return String(path || '')\r\n      .split('?')[0]\r\n      .split('#')[0]\r\n      .replace(\/\\\/+$\/, '')\r\n      .toLowerCase();\r\n  }\r\n\r\n  function highlightActive() {\r\n    var sidebar = document.querySelector('.ols-sidebar');\r\n    if (!sidebar) return false;\r\n\r\n    var currentPath = normalisePath(window.location.pathname);\r\n    var links = sidebar.querySelectorAll('a[href]');\r\n    var matched = null;\r\n    var matchedLength = 0;\r\n\r\n    sidebar.querySelectorAll('.active, .active-main, .parent-active').forEach(function(item) {\r\n      item.classList.remove('active', 'active-main', 'parent-active');\r\n    });\r\n\r\n    sidebar.querySelectorAll('a[data-ols-disabled-parent=\"1\"], 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true;\r\n  }\r\n\r\n  if (!highlightActive()) {\r\n    document.addEventListener('DOMContentLoaded', highlightActive);\r\n  }\r\n})();\r\n<\/script>\n\n  <main class=\"ols-main\">\n      <nav class=\"ols-breadcrumbs\" aria-label=\"Breadcrumb\">\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\">Revision Notes<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\">A Level Chemistry<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/\">AQA<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/\">3.1.3 Bonding<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/\">Intermolecular Forces<\/a> \/\n<span>Hydrogen Bonding<\/span>\n<\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Hydrogen Bonding<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to hydrogen bonding: the N-H, O-H and H-F requirement, the four features of the exam diagram, hydrogen bonding in water, ammonia and hydrogen fluoride, and predicting it in other molecules, for AQA A Level Chemistry.<\/p>\n\n        <div class=\"ols-badges\">\n<div class=\"ols-badge\">Paper 1 and 2 AQA<\/div>\n<div class=\"ols-badge\">3.1.3 Bonding<\/div>\n<div class=\"ols-badge\">7405\/1 and 7405\/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      <article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">1<\/div>\n<h2>What a Hydrogen Bond Is<\/h2>\n<\/div>\n<p>A <strong>hydrogen bond<\/strong> is a strong intermolecular attraction between a hydrogen atom that is covalently bonded to nitrogen, oxygen or fluorine in one molecule and a <strong>lone pair<\/strong> of electrons on a nitrogen, oxygen or fluorine atom in a neighbouring molecule. It is the strongest of the three intermolecular forces, but it is still far weaker than a covalent bond.<\/p>\n<p>Three things make the bond possible. Nitrogen, oxygen and fluorine are the three most electronegative elements, so the H atom bonded to one of them carries a large \u03b4+ charge. The hydrogen atom is tiny and has no inner electrons, so its \u03b4+ charge is concentrated and can approach a neighbouring atom very closely. The N, O or F atom on the neighbour has a lone pair that points its negative charge directly at the \u03b4+ hydrogen. The result is a directional attraction, with the X-H\u00b7\u00b7\u00b7Y atoms in a straight line, that is much stronger than an ordinary permanent dipole-dipole attraction.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Definition:<\/strong> A hydrogen bond forms between a \u03b4+ hydrogen atom bonded to N, O or F and a lone pair on N, O or F in another molecule.<\/p>\n<\/div>\n<\/article>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">2<\/div>\n<h2>The Exam Diagram<\/h2>\n<\/div>\n<p>Questions that ask you to <em>show<\/em> hydrogen bonding are marked on four features, and a diagram that misses any of them loses marks:<\/p>\n<ol>\n<li>The <strong>lone pair<\/strong> drawn on the N, O or F atom that accepts the bond.<\/li>\n<li><strong>\u03b4+<\/strong> on the hydrogen and <strong>\u03b4-<\/strong> on the electronegative atom in both molecules.<\/li>\n<li>The hydrogen bond drawn as a <strong>dashed line<\/strong> from the \u03b4+ H to the lone pair, and labelled.<\/li>\n<li>The three atoms X-H\u00b7\u00b7\u00b7Y in a <strong>straight line<\/strong> (a 180\u00b0 arrangement), with the water molecule kept bent.<\/li>\n<\/ol>\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\/hydrogen-bonding-in-water-ammonia-and-hydrogen-fluoride.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\/hydrogen-bonding-in-water-ammonia-and-hydrogen-fluoride.jpg\" alt=\"Exam-style hydrogen bond diagrams for water, ammonia and hydrogen fluoride with lone pairs, partial charges and dashed hydrogen bonds\">\n<\/a>\n<\/div>\n<div class=\"ols-zoom-card-caption\"><p>The four marked features of a hydrogen bond diagram: lone pair, \u03b4 charges, a labelled dashed line and a straight X-H\u00b7\u00b7\u00b7Y arrangement.<\/p><\/div>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Exam trap:<\/strong> The dashed line must start at the hydrogen atom and end at the lone pair, not at the O, N or F atom in general. Draw the lone pair first, then the line to it.<\/p>\n<\/div>\n<\/article>\n<article class=\"ols-note-card purple\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">3<\/div>\n<h2>Hydrogen Bonding in Water<\/h2>\n<\/div>\n<p>Each water molecule has two O-H bonds and two lone pairs on the oxygen, so each molecule can form up to <strong>four<\/strong> hydrogen bonds: two through its own hydrogen atoms and two through its lone pairs. In liquid water the molecules form a constantly changing network of hydrogen bonds; in ice the network becomes a fixed, open lattice (see the <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/anomalous-properties-of-water\/\">Anomalous Properties of Water<\/a> page).<\/p>\n<section class=\"ols-hb-001\" id=\"olsHb001\">\n<style>\n@import url('https:\/\/fonts.googleapis.com\/css2?family=Poppins:wght@300;400;500;600&display=swap');\n\n.ols-hb-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-hb-001 *{box-sizing:border-box;}\n\n.ols-hb-001 .hb-head{margin:0 0 22px;}\n.ols-hb-001 h2.hb-title{\n  font-size:26px; 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font-size:13px;}\n  .ols-hb-001 .hb-lab{font-size:10.5px; padding:4px 8px;}\n  .ols-hb-001 .hb-lab.l-ang{font-size:12px;}\n  .ols-hb-001 .hb-caption{font-size:10.5px; padding:5px 9px; max-width:66%;}\n  .ols-hb-001 .hb-info{padding:18px;}\n}\n@media (prefers-reduced-motion:reduce){\n  .ols-hb-001 .hb-seg button,.ols-hb-001 .hb-pill{transition:none;}\n}\n\n.ols-cc-hb-001{\n  font-family:'Poppins',system-ui,-apple-system,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;\n  margin:10px auto 0; text-align:center; font-size:11px; font-style:italic; color:#aab0c0;\n}\n.ols-cc-hb-001 a{color:#aab0c0; text-decoration:none;}\n.ols-cc-hb-001 a:hover{text-decoration:underline;}\n<\/style>\n\n<div class=\"hb-head\">\n  <h2 class=\"hb-title\">Hydrogen Bonding in Water: Four Neighbours in a Tetrahedral Arrangement<\/h2>\n  <p class=\"hb-sub\">Drag to rotate, scroll or pinch to zoom. Start with one water molecule and its two lone pairs, then add the four neighbours it can hydrogen bond to. The four bonds point to the corners of a tetrahedron.<\/p>\n<\/div>\n\n<div class=\"hb-stage\" id=\"hbStage\">\n  <canvas class=\"hb-canvas\" id=\"hbCanvas\"><\/canvas>\n  <div class=\"hb-overlay\" id=\"hbOverlay\"><\/div>\n  <div class=\"hb-caption\" id=\"hbCaption\"><\/div>\n  <div class=\"hb-hint\" id=\"hbHint\">Drag to rotate<\/div>\n<\/div>\n\n<div class=\"hb-controls\">\n  <div class=\"hb-row\">\n    <span class=\"hb-rowlab\">Show<\/span>\n    <div class=\"hb-seg\" role=\"group\" aria-label=\"What to show\">\n      <button type=\"button\" data-s=\"one\" aria-pressed=\"true\">One molecule<\/button>\n      <button type=\"button\" data-s=\"four\" aria-pressed=\"false\">Four neighbours<\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"hb-row\">\n    <span class=\"hb-rowlab\">View<\/span>\n    <div class=\"hb-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=\"corner\" aria-pressed=\"false\">Corner<\/button>\n      <button type=\"button\" data-v=\"top\" aria-pressed=\"false\">Top<\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"hb-row\">\n    <span class=\"hb-rowlab\">Detail<\/span>\n    <button type=\"button\" class=\"hb-pill p-rose\" id=\"hbTogLp\" aria-pressed=\"true\"><i class=\"dot\"><\/i>Lone pairs<\/button>\n    <button type=\"button\" class=\"hb-pill\" id=\"hbTogD\" aria-pressed=\"true\"><i class=\"dot\"><\/i>&delta; charges<\/button>\n    <button type=\"button\" class=\"hb-pill\" id=\"hbTogA\" aria-pressed=\"true\"><i class=\"dot\"><\/i>Angles<\/button>\n    <button type=\"button\" class=\"hb-pill\" id=\"hbTogL\" aria-pressed=\"true\"><i class=\"dot\"><\/i>Labels<\/button>\n  <\/div>\n\n  <div class=\"hb-row\">\n    <span class=\"hb-rowlab\">Motion<\/span>\n    <button type=\"button\" class=\"hb-pill\" id=\"hbSpin\" aria-pressed=\"false\"><i class=\"dot\"><\/i>Rotation<\/button>\n    <button type=\"button\" class=\"hb-pill\" id=\"hbResetV\">Reset view<\/button>\n  <\/div>\n<\/div>\n\n<div class=\"hb-info\">\n  <h3 id=\"hbInfoTitle\"><\/h3>\n  <p id=\"hbInfoText\"><\/p>\n  <div class=\"hb-facts\" id=\"hbFacts\"><\/div>\n  <div class=\"hb-key\">\n    <span><i style=\"background:rgba(198,46,40,0.85)\"><\/i>Oxygen, &delta;&minus;<\/span>\n    <span><i style=\"background:rgba(226,229,238,0.95)\"><\/i>Hydrogen, &delta;+<\/span>\n    <span><i style=\"background:rgba(198,62,122,0.5)\"><\/i>Lone pair<\/span>\n    <span><i style=\"background:rgba(37,99,235,0.55)\"><\/i>Hydrogen bond<\/span>\n  <\/div>\n<\/div>\n<\/section>\n\n<p class=\"ols-cc-hb-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\/water-hydrogen-bonding.js\"><\/script>\n<p>Because water forms so many hydrogen bonds per molecule, its boiling point is far higher than that of any hydride of similar size, and it takes a great deal of energy to boil.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> Two O-H bonds plus two lone pairs give water the maximum of four hydrogen bonds per molecule; this is the root of every anomalous property of water.<\/p>\n<\/div>\n<\/article>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">4<\/div>\n<h2>Hydrogen Bonding in Ammonia and Hydrogen Fluoride<\/h2>\n<\/div>\n<p><strong>Ammonia, NH\u2083,<\/strong> has three N-H bonds but only <strong>one lone pair<\/strong> on nitrogen. Each molecule can therefore be involved in hydrogen bonds through its hydrogens, but only one neighbour at a time can bond to its lone pair, so on average liquid ammonia has about one hydrogen bond per molecule. Nitrogen is also less electronegative than oxygen, so the N-H hydrogen is less \u03b4+ and the bond is weaker. Ammonia boils at -33 \u00b0C.<\/p>\n<p><strong>Hydrogen fluoride, HF,<\/strong> has three lone pairs on fluorine but only <strong>one hydrogen<\/strong>, so again each molecule averages one hydrogen bond, forming zig-zag chains of molecules. Fluorine is the most electronegative element, so each individual F-H\u00b7\u00b7\u00b7F bond is the strongest hydrogen bond of all, and HF boils at 20 \u00b0C, far above HCl at -85 \u00b0C.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Liquid<\/th><th>H atoms on N, O or F<\/th><th>Lone pairs<\/th><th>Hydrogen bonds per molecule (average)<\/th><th>boiling point \/ \u00b0C<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>H\u2082O<\/strong><\/td><td>2<\/td><td>2<\/td><td>up to 4, about 3.5 in the liquid<\/td><td>100<\/td><\/tr>\n<tr><td><strong>HF<\/strong><\/td><td>1<\/td><td>3<\/td><td>about 1 (chains)<\/td><td>20<\/td><\/tr>\n<tr><td><strong>NH\u2083<\/strong><\/td><td>3<\/td><td>1<\/td><td>about 1<\/td><td>-33<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>The order of boiling points, H\u2082O > HF > NH\u2083, follows the number of hydrogen bonds each molecule can make more closely than the strength of each bond. The <strong>number<\/strong> of hydrogen bonds is limited by whichever is fewer: suitable hydrogens or lone pairs.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Exam sentence:<\/strong> Water has a higher boiling point than ammonia because each water molecule can form more hydrogen bonds (two O-H bonds and two lone pairs) and O-H\u00b7\u00b7\u00b7O hydrogen bonds are stronger than N-H\u00b7\u00b7\u00b7N bonds, so more energy is needed to separate the molecules.<\/p>\n<\/div>\n<\/article>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">5<\/div>\n<h2>Predicting Hydrogen Bonding in Other Molecules<\/h2>\n<\/div>\n<p>The test is simple and should be applied literally: <strong>is there a hydrogen atom bonded directly to N, O or F?<\/strong> If yes, the substance forms hydrogen bonds between its molecules. If the only N, O or F atoms are bonded to carbon, the molecule may accept a hydrogen bond from water but cannot form one with its own kind.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Molecule<\/th><th>H on N, O or F?<\/th><th>Hydrogen bonds between its own molecules?<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Methanol, CH\u2083OH<\/strong><\/td><td>yes (O-H)<\/td><td>yes<\/td><\/tr>\n<tr><td><strong>Methylamine, CH\u2083NH\u2082<\/strong><\/td><td>yes (N-H)<\/td><td>yes<\/td><\/tr>\n<tr><td><strong>Ethanoic acid, CH\u2083COOH<\/strong><\/td><td>yes (O-H)<\/td><td>yes, in pairs (dimers)<\/td><\/tr>\n<tr><td><strong>Fluoromethane, CH\u2083F<\/strong><\/td><td>no (F on C, H on C)<\/td><td>no<\/td><\/tr>\n<tr><td><strong>Methoxymethane, CH\u2083OCH\u2083<\/strong><\/td><td>no<\/td><td>no, but accepts from water<\/td><\/tr>\n<tr><td><strong>Ethanal, CH\u2083CHO<\/strong><\/td><td>no<\/td><td>no, but accepts from water<\/td><\/tr>\n<tr><td><strong>Hydrogen chloride, HCl<\/strong><\/td><td>no (Cl is not N, O or F)<\/td><td>no<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>Molecules of biological importance rely on this bond: the two strands of DNA are held together by hydrogen bonds between base pairs, proteins fold because of hydrogen bonds between N-H and C=O groups, and the hydroxyl groups of sugars make them soluble in water.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Common mistake:<\/strong> Assuming any molecule that contains oxygen forms hydrogen bonds. Propanone and ethers contain oxygen but no O-H, so they do not hydrogen bond with each other.<\/p>\n<\/div>\n<\/article>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">6<\/div>\n<h2>Hydrogen Bonds Compared With Other Forces<\/h2>\n<\/div>\n<p>A hydrogen bond typically needs 10 to 40 kJ mol\u207b\u00b9 to break, roughly ten times a small permanent dipole-dipole attraction and a tenth of a covalent bond. It is still an <strong>intermolecular<\/strong> force: when water boils, hydrogen bonds break and the O-H covalent bonds do not.<\/p>\n<p>Hydrogen bonds act in addition to permanent dipole-dipole forces and induced dipole-dipole forces, so a hydrogen-bonded liquid has all three forces between its molecules. In a small molecule such as water the hydrogen bonds dominate; in a large molecule such as hexan-1-ol the induced dipole-dipole forces along the carbon chain contribute as much or more.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Exam wording:<\/strong> Call it a hydrogen bond, not a &#8220;hydrogen bonding force&#8221; or a &#8220;covalent hydrogen bond&#8221;. State that it is intermolecular.<\/p>\n<\/div>\n<\/article>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">7<\/div>\n<h2>Common Exam Points<\/h2>\n<\/div>\n<h3>Draw hydrogen bonding between two molecules of X<\/h3><p>Lone pair on N, O or F; \u03b4+ and \u03b4-; dashed line labelled hydrogen bond from H to the lone pair; straight X-H\u00b7\u00b7\u00b7Y arrangement.<\/p>\n<h3>Explain why HF boils higher than HCl<\/h3><p>HF forms hydrogen bonds (F is highly electronegative and has lone pairs); HCl cannot; hydrogen bonds are stronger than the permanent dipole-dipole forces in HCl, so more energy is needed.<\/p>\n<h3>Does molecule X form hydrogen bonds?<\/h3><p>Only if it has H bonded directly to N, O or F. Oxygen bonded to carbon alone is not enough.<\/p>\n<h3>Do not say<\/h3><p>&#8220;Hydrogen bonds are covalent&#8221;; &#8220;hydrogen bonds form between hydrogen atoms&#8221;; &#8220;the O-H bond breaks when water boils&#8221;.<\/p>\n<\/article>\n<section class=\"ols-h5p-card\">\n<h2>Check Your Understanding<\/h2>\n<p>Check that you can spot hydrogen bonding and draw it correctly for molecules other than water, ammonia and hydrogen fluoride.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-530\" class=\"h5p-iframe\" data-content-id=\"530\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"IMF Hydrogen Bonding Drag: ethylamine and hydrogen sulfide\"><\/iframe><\/div><\/div>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-531\" class=\"h5p-iframe\" data-content-id=\"531\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"IMF Hydrogen Bonding MCQ: which forms hydrogen bonds\"><\/iframe><\/div><\/div>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-532\" class=\"h5p-iframe\" data-content-id=\"532\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"IMF Hydrogen Bonding MCQ: the diagram\"><\/iframe><\/div><\/div>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-533\" class=\"h5p-iframe\" data-content-id=\"533\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"IMF Hydrogen Bonding MCQ: phosphine and ammonia\"><\/iframe><\/div><\/div>\n<\/section>\n<section class=\"ols-faq-card\">\n<h2>FAQs<\/h2>\n<p>Use these quick answers to check the hydrogen bonding rules and the diagram marks in AQA A Level Chemistry questions.<\/p>\n\n<div class=\"ols-faq-list\">\n<div class=\"ols-faq-item\">\n<h3>When does hydrogen bonding occur?<\/h3>\n<p>Only when a hydrogen atom is bonded directly to nitrogen, oxygen or fluorine, and there is a lone pair on an N, O or F atom in a neighbouring molecule to accept it. Those three elements are electronegative enough to leave the hydrogen strongly \u03b4+.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>What must a hydrogen bond diagram show?<\/h3>\n<p>Four things: the lone pair on the accepting atom, \u03b4+ and \u03b4- labels, a dashed line drawn from the \u03b4+ hydrogen to that lone pair, and the three atoms X-H\u00b7\u00b7\u00b7Y in a straight line.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>How many hydrogen bonds can one water molecule form?<\/h3>\n<p>Four: two through its own hydrogen atoms and two through the two lone pairs on its oxygen. This is more than ammonia or hydrogen fluoride can manage and explains why water is the most anomalous of the three.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Does a molecule that contains oxygen always hydrogen bond?<\/h3>\n<p>No. Propanone and methoxymethane contain oxygen but have no O-H group, so their molecules cannot hydrogen bond with each other. They can still accept a hydrogen bond from water, which is why they dissolve in it.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Is a hydrogen bond a covalent bond?<\/h3>\n<p>No. It is an intermolecular force, roughly a tenth the strength of a covalent bond. When water boils the hydrogen bonds break and every O-H covalent bond stays intact.<\/p>\n<\/div>\n<\/div>\n<\/section>\n<section class=\"ols-related-card\">\n<h2>Related Intermolecular Forces Pages<\/h2>\n<p>Use these pages to connect the three intermolecular forces with the physical properties they explain.<\/p>\n<div class=\"ols-related-grid\">\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/london-forces\/\">London Forces<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/permanent-dipole-dipole-forces\/\">Permanent Dipole-Dipole Forces<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/anomalous-properties-of-water\/\">Anomalous Properties of Water<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/boiling-temperature-trends\/\">Boiling Point Trends<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/intermolecular-forces\/choosing-solvents\/\">Choosing Solvents<\/a>\n<\/div>\n<\/section>\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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