{"id":4682,"date":"2026-06-01T12:06:07","date_gmt":"2026-06-01T11:06:07","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/"},"modified":"2026-10-24T19:51:11","modified_gmt":"2026-10-24T18:51:11","slug":"group-7-halogens","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/","title":{"rendered":"Group 7 Halogens"},"content":{"rendered":"\n<div class=\"ols-t4-page\">\n\n  <aside class=\"ols-sidebar\">\n  <div class=\"ols-sidebar-header\">\n    <h3>Revision Notes<\/h3>\n    <p>A Level Chemistry<\/p>\n  <\/div>\n\n  <div class=\"ols-topic-group\">\n    <h4>Topic 4 Inorganic Chemistry and The Periodic Table<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/\">Topic 4 Overview<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/groups-1-and-2\/\">Groups 1 and 2<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/groups-1-and-2\/trends-down-groups-1-and-2\/\">Trends Down Groups 1 and 2<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/groups-1-and-2\/reactions-of-the-group-1-and-2-elements\/\">Reactions of the Group 1 and 2 Elements<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/groups-1-and-2\/oxides-hydroxides-and-carbonates\/\">Oxides, Hydroxides and Carbonates<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/groups-1-and-2\/solubility-trends-and-the-sulfate-test\/\">Solubility Trends and the Sulfate Test<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/groups-1-and-2\/thermal-stability-and-flame-colours\/\">Thermal Stability and Flame Colours<\/a>\n          <\/li>\n        <\/ul>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/\">Group 7 Halogens<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/trends-in-the-halogens\/\">Trends in the Halogens<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/halogens-as-oxidising-agents\/\">Halogens as Oxidising Agents<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/disproportionation-reactions-of-chlorine\/\">Disproportionation Reactions of Chlorine<\/a>\n          <\/li>\n          <li>\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/halide-ions-reducing-agents-and-tests\/\">Halide Ions: Reducing Agents and Tests<\/a>\n          <\/li>\n        <\/ul>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/inorganic-analysis\/\">Inorganic Analysis: Tests for Ions<\/a>\n      <\/li>\n    <\/ul>\n  <\/div>\n\n  <div class=\"ols-topic-group\">\n    <h4>Next Topics<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-5-formulae-equations-and-amounts-of-substance\/\">Topic 5 Formulae, Equations &amp; Amounts<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/\">Topic 6 Organic Chemistry I<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-7-modern-analytical-techniques-i\/\">Topic 7 Modern Analytical Techniques I<\/a>\n      <\/li>\n    <\/ul>\n  <\/div>\n<\/aside>\n\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\"], a[aria-current]').forEach(function(a) {\r\n      a.removeAttribute('aria-current');\r\n      a.removeAttribute('tabindex');\r\n      a.removeAttribute('data-ols-disabled-parent');\r\n    });\r\n\r\n    links.forEach(function(a) {\r\n      try {\r\n        var href = a.getAttribute('href');\r\n        if (!href || href === '#' || href.charAt(0) === '#') return;\r\n        var linkPath = normalisePath(new URL(href, window.location.origin).pathname);\r\n        if (!linkPath) return;\r\n        if (currentPath === linkPath || currentPath.indexOf(linkPath + '\/') === 0) {\r\n          if (linkPath.length > matchedLength) {\r\n            matched = a;\r\n            matchedLength = linkPath.length;\r\n          }\r\n        }\r\n      } catch(e) {}\r\n    });\r\n\r\n    if (matched) {\r\n      var matchedLi = matched.closest('li');\r\n      var parentSub = matched.closest('.ols-subtopic-list');\r\n\r\n      if (parentSub) {\r\n        if (matchedLi) {\r\n          matchedLi.classList.add('active');\r\n          matched.setAttribute('aria-current', 'page');\r\n        }\r\n        var parentLi = parentSub.closest('li');\r\n        if (parentLi) {\r\n          parentLi.classList.add('parent-active', 'active-main');\r\n          var parentLink = parentLi.querySelector(':scope > a');\r\n          if (parentLink) {\r\n            parentLink.setAttribute('aria-current', 'true');\r\n            parentLink.setAttribute('tabindex', '-1');\r\n            parentLink.setAttribute('data-ols-disabled-parent', '1');\r\n          }\r\n        }\r\n      } else {\r\n        if (matchedLi) {\r\n          matchedLi.classList.add('parent-active', 'active-main');\r\n          matched.setAttribute('aria-current', 'page');\r\n          matched.setAttribute('tabindex', '-1');\r\n          matched.setAttribute('data-ols-disabled-parent', '1');\r\n        }\r\n      }\r\n    }\r\n\r\n    return true;\r\n  }\r\n\r\n  if (!highlightActive()) {\r\n    document.addEventListener('DOMContentLoaded', highlightActive);\r\n  }\r\n})();\r\n<\/script>\n\n  <style>\n    @import url('https:\/\/fonts.googleapis.com\/css2?family=Poppins:wght@300;400;500;600;700;800&display=swap');\n\n    .ols-t4-page,\n    .ols-t4-page * {\n      box-sizing: border-box;\n    }\n\n    .ols-t4-page {\n      --ols-navy: #1C244B;\n      --ols-blue: #467FF7;\n      --ols-soft-blue: #EEF4FF;\n      --ols-border: rgba(28, 36, 75, 0.12);\n      --ols-shadow: 0 18px 45px rgba(28, 36, 75, 0.12);\n      --ols-shadow-soft: 0 10px 28px rgba(28, 36, 75, 0.09);\n      --ols-muted: #4b5575;\n      font-family: \"Poppins\", Arial, sans-serif;\n      color: var(--ols-navy);\n      background: #ffffff;\n    }\n\n    .ols-t4-page a {\n      color: inherit;\n      text-decoration: none;\n    }\n\n    .ols-t4-container {\n      width: min(1180px, calc(100% - 40px));\n      margin: 0 auto;\n    }\n\n    \/* =========================================================\n       BREADCRUMB BAR\n    ========================================================= *\/\n\n    .ols-t4-breadcrumb-bar {\n      padding: 16px 0 0;\n    }\n\n    .ols-t4-breadcrumb {\n      display: flex;\n      flex-wrap: wrap;\n      gap: 6px;\n      font-size: 13px;\n      color: var(--ols-muted);\n      font-weight: 500;\n    }\n\n    .ols-t4-breadcrumb a {\n      color: var(--ols-muted);\n      transition: color 0.2s ease;\n    }\n\n    .ols-t4-breadcrumb a:hover {\n      color: var(--ols-blue);\n    }\n\n    .ols-t4-breadcrumb span {\n      color: var(--ols-navy);\n      font-weight: 700;\n    }\n\n    \/* =========================================================\n       INTRO \/ HERO\n    ========================================================= *\/\n\n    .ols-t4-intro {\n      padding: 36px 0 72px;\n      background:\n        radial-gradient(circle at top center, rgba(70, 127, 247, 0.07), transparent 40%),\n        linear-gradient(180deg, #f7f9fd 0%, #ffffff 100%);\n    }\n\n    .ols-t4-intro-inner {\n      display: grid;\n      grid-template-columns: 1fr 1fr;\n      gap: 64px;\n      align-items: center;\n    }\n\n    .ols-t4-eyebrow {\n      display: inline-flex;\n      align-items: center;\n      gap: 9px;\n      padding: 8px 16px;\n      border-radius: 999px;\n      background: #ffffff;\n      border: 1px solid rgba(70, 127, 247, 0.20);\n      color: var(--ols-blue);\n      font-size: 13px;\n      font-weight: 600;\n      box-shadow: 0 6px 18px rgba(28, 36, 75, 0.06);\n      margin-bottom: 20px;\n    }\n\n    .ols-t4-eyebrow::before {\n      content: \"\";\n      width: 7px;\n      height: 7px;\n      border-radius: 50%;\n      background: var(--ols-blue);\n      box-shadow: 0 0 0 4px rgba(70, 127, 247, 0.14);\n    }\n\n    .ols-t4-intro h1 {\n      font-size: clamp(34px, 4.5vw, 64px);\n      font-weight: 800;\n      color: var(--ols-navy);\n      letter-spacing: -0.045em;\n      line-height: 1.08;\n      margin: 0 0 10px;\n      text-shadow: -9px 0 9px rgba(28, 36, 75, 0.08);\n    }\n\n    .ols-t4-accent-bar {\n      width: 72px;\n      height: 4px;\n      background: var(--ols-blue);\n      border-radius: 999px;\n      margin: 0 0 22px;\n    }\n\n    .ols-t4-intro-lead {\n      font-size: clamp(16px, 1.6vw, 19px);\n      font-weight: 300;\n      color: #11316b;\n      line-height: 1.72;\n      margin: 0;\n    }\n\n    .ols-t4-info-grid {\n      display: grid;\n      grid-template-columns: 1fr 1fr;\n      gap: 14px;\n    }\n\n    .ols-t4-info-card {\n      background: #ffffff;\n      border: 1px solid var(--ols-border);\n      border-radius: 20px;\n      padding: 20px 22px;\n      box-shadow: var(--ols-shadow-soft);\n    }\n\n    .ols-t4-info-card-label {\n      font-size: 11px;\n      font-weight: 700;\n      text-transform: uppercase;\n      letter-spacing: 0.06em;\n      color: var(--ols-muted);\n      margin-bottom: 6px;\n    }\n\n    .ols-t4-info-card-value {\n      font-size: 22px;\n      font-weight: 800;\n      color: var(--ols-navy);\n      letter-spacing: -0.03em;\n      line-height: 1.1;\n    }\n\n    .ols-t4-info-card-sub {\n      font-size: 12px;\n      font-weight: 400;\n      color: var(--ols-muted);\n      margin-top: 3px;\n    }\n\n    \/* =========================================================\n       TOPIC CARDS SECTION\n    ========================================================= *\/\n\n    .ols-t4-topics {\n      padding: 72px 0 80px;\n      background: #ffffff;\n    }\n\n    .ols-t4-section-header {\n      margin-bottom: 40px;\n    }\n\n    .ols-t4-section-title {\n      font-size: clamp(28px, 3vw, 44px);\n      font-weight: 800;\n      color: var(--ols-navy);\n      letter-spacing: -0.04em;\n      line-height: 1.1;\n      margin: 0 0 10px;\n      text-shadow: -9px 0 9px rgba(28, 36, 75, 0.08);\n    }\n\n    .ols-t4-section-sub {\n      font-size: 16px;\n      font-weight: 300;\n      color: var(--ols-muted);\n      margin: 0;\n    }\n\n    .ols-t4-cards-grid {\n      display: grid;\n      grid-template-columns: repeat(3, minmax(0, 1fr));\n      gap: 20px;\n    }\n\n    .ols-t4-card {\n      display: flex;\n      flex-direction: column;\n      background: #ffffff;\n      border: 1px solid var(--ols-border);\n      border-radius: 22px;\n      overflow: hidden;\n      box-shadow: var(--ols-shadow-soft);\n      text-decoration: none;\n      color: var(--ols-navy);\n      transition:\n        transform 0.28s cubic-bezier(0.34, 1.56, 0.64, 1),\n        box-shadow 0.28s ease,\n        border-color 0.28s ease;\n      position: relative;\n    }\n\n    .ols-t4-card.ols-t4-card--available:hover {\n      transform: translateY(-10px) scale(1.02);\n      box-shadow: 0 28px 56px rgba(28, 36, 75, 0.16);\n      border-color: rgba(70, 127, 247, 0.35);\n    }\n\n    .ols-t4-card.ols-t4-card--available:hover .ols-t4-card-img-wrap::after {\n      opacity: 1;\n    }\n\n    .ols-t4-card-img-wrap {\n      position: relative;\n      width: 100%;\n      aspect-ratio: 4 \/ 3;\n      background: var(--ols-soft-blue);\n      overflow: hidden;\n    }\n\n    .ols-t4-card-img-wrap::after {\n      content: \"\";\n      position: absolute;\n      inset: 0;\n      background: linear-gradient(180deg, transparent 40%, rgba(28, 36, 75, 0.20) 100%);\n      opacity: 0;\n      transition: opacity 0.28s ease;\n      z-index: 1;\n    }\n\n    .ols-t4-card-num {\n      position: absolute;\n      top: 12px;\n      left: 12px;\n      width: 32px;\n      height: 32px;\n      border-radius: 50%;\n      background: var(--ols-navy);\n      color: #ffffff;\n      font-size: 13px;\n      font-weight: 800;\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      z-index: 3;\n      box-shadow: 0 4px 12px rgba(28, 36, 75, 0.28);\n    }\n\n    .ols-t4-card-status {\n      position: absolute;\n      top: 12px;\n      right: 12px;\n      padding: 4px 10px;\n      border-radius: 999px;\n      font-size: 10px;\n      font-weight: 700;\n      z-index: 3;\n    }\n\n    .ols-t4-card-status--available {\n      background: #eaf3de;\n      color: #3B6D11;\n    }\n\n    .ols-t4-card-body {\n      padding: 18px 18px 22px;\n      flex: 1;\n      display: flex;\n      flex-direction: column;\n      gap: 6px;\n    }\n\n    .ols-t4-card-title {\n      font-size: 14px;\n      font-weight: 700;\n      color: var(--ols-navy);\n      line-height: 1.35;\n      margin: 0;\n    }\n\n    .ols-t4-card-desc {\n      font-size: 12px;\n      font-weight: 300;\n      color: var(--ols-muted);\n      line-height: 1.6;\n      margin: 0;\n    }\n\n    .ols-t4-card-cta {\n      display: inline-flex;\n      align-items: center;\n      gap: 5px;\n      margin-top: 10px;\n      font-size: 12px;\n      font-weight: 700;\n      color: var(--ols-blue);\n    }\n\n    .ols-t4-card-cta svg {\n      width: 14px;\n      height: 14px;\n      transition: transform 0.2s ease;\n    }\n\n    .ols-t4-card--available:hover .ols-t4-card-cta svg {\n      transform: translateX(3px);\n    }\n\n    .ols-t4-visual {\n      position: absolute;\n      inset: 0;\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      padding: 32px 24px 24px;\n      overflow: hidden;\n    }\n\n    .ols-t4-visual::before,\n    .ols-t4-visual::after {\n      content: \"\";\n      position: absolute;\n      border-radius: 999px;\n      opacity: 0.75;\n      filter: blur(1px);\n    }\n\n    .ols-t4-visual::before {\n      width: 170px;\n      height: 170px;\n      left: -58px;\n      bottom: -66px;\n      background: rgba(255, 255, 255, 0.35);\n    }\n\n    .ols-t4-visual::after {\n      width: 118px;\n      height: 118px;\n      right: -42px;\n      top: -34px;\n      background: rgba(255, 255, 255, 0.28);\n    }\n\n    .ols-t4-visual-panel {\n      position: relative;\n      z-index: 2;\n      width: min(82%, 260px);\n      min-height: 118px;\n      border-radius: 24px;\n      border: 1px solid rgba(255, 255, 255, 0.45);\n      background: rgba(255, 255, 255, 0.76);\n      box-shadow: 0 18px 38px rgba(28, 36, 75, 0.18);\n      backdrop-filter: blur(10px);\n      display: flex;\n      flex-direction: column;\n      align-items: center;\n      justify-content: center;\n      text-align: center;\n      padding: 18px;\n    }\n\n    .ols-t4-visual-kicker {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      min-height: 25px;\n      padding: 4px 10px;\n      border-radius: 999px;\n      background: rgba(28, 36, 75, 0.08);\n      color: var(--ols-navy);\n      font-size: 10px;\n      font-weight: 800;\n      text-transform: uppercase;\n      letter-spacing: 0.08em;\n      margin-bottom: 10px;\n    }\n\n    .ols-t4-visual-main {\n      font-size: clamp(24px, 3vw, 34px);\n      font-weight: 800;\n      color: var(--ols-navy);\n      line-height: 1.05;\n      letter-spacing: -0.05em;\n    }\n\n    .ols-t4-visual-sub {\n      font-size: 11px;\n      font-weight: 500;\n      color: #4b5575;\n      line-height: 1.45;\n      margin-top: 8px;\n    }\n\n    .ols-t4-visual--ionic {\n      background:\n        radial-gradient(circle at 24% 18%, rgba(255,255,255,0.42), transparent 24%),\n        linear-gradient(135deg, #eef6ff 0%, #8fb9ff 45%, #467FF7 100%);\n    }\n\n    .ols-t4-visual--covalent {\n      background:\n        radial-gradient(circle at 22% 18%, rgba(255,255,255,0.42), transparent 24%),\n        linear-gradient(135deg, #f4ecff 0%, #b997ff 45%, #7356d8 100%);\n    }\n\n    .ols-t4-visual--shape {\n      background:\n        radial-gradient(circle at 24% 18%, rgba(255,255,255,0.42), transparent 24%),\n        linear-gradient(135deg, #eefbf3 0%, #69c98b 45%, #1f7f50 100%);\n    }\n\n    .ols-t4-visual--metallic {\n      background:\n        radial-gradient(circle at 22% 18%, rgba(255,255,255,0.35), transparent 24%),\n        linear-gradient(135deg, #f7f4ed 0%, #b59b75 45%, #4a3623 100%);\n    }\n\n    .ols-t4-molecule-row {\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      gap: 9px;\n      margin-top: 11px;\n      flex-wrap: wrap;\n    }\n\n    .ols-t4-atom {\n      width: 24px;\n      height: 24px;\n      border-radius: 50%;\n      background: #ffffff;\n      border: 1px solid rgba(28, 36, 75, 0.16);\n      box-shadow: 0 6px 14px rgba(28, 36, 75, 0.12);\n    }\n\n    .ols-t4-ion {\n      min-width: 30px;\n      height: 30px;\n      border-radius: 50%;\n      background: #ffffff;\n      border: 1px solid rgba(28, 36, 75, 0.16);\n      box-shadow: 0 6px 14px rgba(28, 36, 75, 0.12);\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      padding: 0 6px;\n      font-size: 11px;\n      font-weight: 800;\n      color: var(--ols-navy);\n    }\n\n    .ols-t4-bond {\n      width: 22px;\n      height: 3px;\n      border-radius: 999px;\n      background: rgba(28, 36, 75, 0.55);\n    }\n\n    .ols-t4-shape {\n      width: 74px;\n      height: 62px;\n      position: relative;\n      margin: 0 auto 12px;\n    }\n\n    .ols-t4-shape span {\n      position: absolute;\n      width: 21px;\n      height: 21px;\n      border-radius: 50%;\n      background: #ffffff;\n      border: 1px solid rgba(28, 36, 75, 0.16);\n      box-shadow: 0 6px 14px rgba(28, 36, 75, 0.12);\n    }\n\n    .ols-t4-shape span:nth-child(1) {\n      left: 27px;\n      top: 20px;\n      background: var(--ols-navy);\n    }\n\n    .ols-t4-shape span:nth-child(2) {\n      left: 0;\n      top: 0;\n    }\n\n    .ols-t4-shape span:nth-child(3) {\n      right: 0;\n      top: 0;\n    }\n\n    .ols-t4-shape span:nth-child(4) {\n      left: 27px;\n      bottom: 0;\n    }\n\n    .ols-t4-electron-dot {\n      width: 12px;\n      height: 12px;\n      border-radius: 50%;\n      background: var(--ols-blue);\n      box-shadow: 0 0 0 7px rgba(70, 127, 247, 0.18);\n      margin: 0 auto 14px;\n    }\n\n\n    .ols-t4-visual--polar {\n      background:\n        radial-gradient(circle at 24% 18%, rgba(255,255,255,0.42), transparent 24%),\n        linear-gradient(135deg, #fff7ed 0%, #f59e0b 45%, #b45309 100%);\n    }\n\n    .ols-t4-visual--intermolecular {\n      background:\n        radial-gradient(circle at 24% 18%, rgba(255,255,255,0.42), transparent 24%),\n        linear-gradient(135deg, #f0f7ff 0%, #38bdf8 45%, #0369a1 100%);\n    }\n\n    .ols-t4-visual--structure {\n      background:\n        radial-gradient(circle at 24% 18%, rgba(255,255,255,0.42), transparent 24%),\n        linear-gradient(135deg, #f5f3ff 0%, #a78bfa 45%, #5b21b6 100%);\n    }\n\n    \/* =========================================================\n       EXTRA VISUAL COLOUR VARIANTS\n    ========================================================= *\/\n\n    .ols-t4-visual--amber {\n      background: radial-gradient(circle at 24% 18%, rgba(255,255,255,0.42), transparent 24%), linear-gradient(135deg, #fff7ed 0%, #f59e0b 45%, #b45309 100%);\n    }\n\n    .ols-t4-visual--teal {\n      background: radial-gradient(circle at 24% 18%, rgba(255,255,255,0.42), transparent 24%), linear-gradient(135deg, #ecfeff 0%, #22d3ee 45%, #0e7490 100%);\n    }\n\n    .ols-t4-visual--rose {\n      background: radial-gradient(circle at 24% 18%, rgba(255,255,255,0.42), transparent 24%), linear-gradient(135deg, #fff1f2 0%, #fb7185 45%, #be123c 100%);\n    }\n\n    .ols-t4-visual--slate {\n      background: radial-gradient(circle at 24% 18%, rgba(255,255,255,0.38), transparent 24%), linear-gradient(135deg, #f8fafc 0%, #94a3b8 45%, #334155 100%);\n    }\n\n    \/* =========================================================\n       SPECIFICATION SECTION\n    ========================================================= *\/\n\n    .ols-t4-spec-section {\n      padding: 72px 0 88px;\n      background:\n        radial-gradient(circle at top center, rgba(70, 127, 247, 0.06), transparent 38%),\n        linear-gradient(180deg, #f7f9fd 0%, #ffffff 100%);\n    }\n\n    .ols-t4-spec-desktop { display: block; }\n    .ols-t4-spec-mobile  { display: none; }\n\n    @media (max-width: 700px) {\n      .ols-t4-spec-desktop { display: none; }\n      .ols-t4-spec-mobile  { display: block; }\n    }\n\n    .ols-t4-spec-wrap {\n      background: #ffffff;\n      border: 1px solid var(--ols-border);\n      border-radius: 26px;\n      padding: 36px;\n      box-shadow: var(--ols-shadow-soft);\n    }\n\n    .ols-t4-spec-pill {\n      display: inline-flex;\n      align-items: center;\n      padding: 7px 14px;\n      border-radius: 999px;\n      background: var(--ols-soft-blue);\n      border: 1px solid rgba(70, 127, 247, 0.20);\n      color: var(--ols-blue);\n      font-size: 12px;\n      font-weight: 700;\n      margin-bottom: 16px;\n    }\n\n    .ols-t4-spec-heading {\n      font-size: clamp(24px, 2.8vw, 36px);\n      font-weight: 800;\n      color: var(--ols-navy);\n      letter-spacing: -0.035em;\n      line-height: 1.12;\n      margin: 0 0 6px;\n      border-left: 5px solid var(--ols-blue);\n      padding-left: 16px;\n    }\n\n    .ols-t4-spec-intro-text {\n      font-size: 16px;\n      font-weight: 300;\n      color: #374151;\n      line-height: 1.8;\n      margin: 14px 0 26px;\n    }\n\n    .ols-t4-spec-group-title {\n      font-size: 20px;\n      font-weight: 800;\n      color: var(--ols-navy);\n      line-height: 1.2;\n      margin: 30px 0 14px;\n      letter-spacing: -0.025em;\n    }\n\n    .ols-t4-spec-group-title:first-of-type {\n      margin-top: 0;\n    }\n\n    .ols-t4-spec-rows {\n      display: flex;\n      flex-direction: column;\n      gap: 12px;\n    }\n\n    .ols-t4-spec-row {\n      display: flex;\n      flex-wrap: nowrap;\n      align-items: stretch;\n      border-radius: 16px;\n      overflow: hidden;\n      box-shadow: 0 4px 12px rgba(0,0,0,0.05);\n    }\n\n    .ols-t4-spec-row--light { background: #ffffff; border: 1px solid rgba(70, 127, 247, 0.18); }\n    .ols-t4-spec-row--mid   { background: #f0f5ff; border: 1px solid rgba(70, 127, 247, 0.22); }\n\n    .ols-t4-spec-code {\n      flex: 0 0 90px;\n      color: #ffffff;\n      font-size: 18px;\n      font-weight: 800;\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      padding: 18px 12px;\n    }\n\n    .ols-t4-spec-code--dark { background: #1C244B; }\n    .ols-t4-spec-code--mid  { background: #2a3a7a; }\n\n    .ols-t4-spec-text {\n      flex: 1;\n      padding: 16px 20px;\n      font-size: 16px;\n      font-weight: 300;\n      line-height: 1.8;\n      color: #374151;\n    }\n\n    .ols-t4-spec-sub-list {\n      display: flex;\n      flex-direction: column;\n      gap: 10px;\n      margin-top: 12px;\n    }\n\n    .ols-t4-spec-sub-row {\n      display: flex;\n      align-items: stretch;\n      background: #ffffff;\n      border: 1px solid rgba(70, 127, 247, 0.15);\n      border-radius: 12px;\n      overflow: hidden;\n    }\n\n    .ols-t4-spec-sub-code {\n      flex: 0 0 70px;\n      background: #93b5f8;\n      color: #0c2060;\n      font-size: 14px;\n      font-weight: 800;\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      padding: 12px 10px;\n    }\n\n    .ols-t4-spec-sub-text {\n      flex: 1;\n      padding: 12px 16px;\n      font-size: 15px;\n      font-weight: 300;\n      line-height: 1.8;\n      color: #4b5563;\n    }\n\n    .ols-t4-spec-note {\n      margin-top: 10px;\n      font-size: 14px;\n      font-weight: 300;\n      color: #6b7280;\n      font-style: italic;\n      line-height: 1.7;\n    }\n\n    .ols-t4-spec-mob-rows {\n      display: flex;\n      flex-direction: column;\n      gap: 12px;\n    }\n\n    .ols-t4-spec-mob-row {\n      border-radius: 16px;\n      overflow: hidden;\n      box-shadow: 0 4px 12px rgba(0,0,0,0.05);\n    }\n\n    .ols-t4-spec-mob-row--light { background: #ffffff; border: 1px solid rgba(70, 127, 247, 0.18); }\n    .ols-t4-spec-mob-row--mid   { background: #f0f5ff; border: 1px solid rgba(70, 127, 247, 0.22); }\n\n    .ols-t4-spec-mob-code {\n      background: #1C244B;\n      color: #ffffff;\n      font-size: 15px;\n      font-weight: 800;\n      text-align: center;\n      height: 34px;\n      line-height: 34px;\n    }\n\n    .ols-t4-spec-mob-code--mid { background: #2a3a7a; }\n\n    .ols-t4-spec-mob-text {\n      padding: 16px 18px;\n      font-size: 15px;\n      font-weight: 300;\n      line-height: 1.8;\n      color: #374151;\n    }\n\n    .ols-t4-spec-mob-sub-list {\n      display: flex;\n      flex-direction: column;\n      gap: 9px;\n      margin-top: 10px;\n    }\n\n    .ols-t4-spec-mob-sub-row {\n      background: #ffffff;\n      border: 1px solid rgba(70, 127, 247, 0.15);\n      border-radius: 12px;\n      overflow: hidden;\n    }\n\n    .ols-t4-spec-mob-sub-code {\n      background: #93b5f8;\n      color: #0c2060;\n      font-size: 13px;\n      font-weight: 800;\n      text-align: center;\n      height: 30px;\n      line-height: 30px;\n    }\n\n    .ols-t4-spec-mob-sub-text {\n      padding: 12px 16px;\n      font-size: 14px;\n      font-weight: 300;\n      line-height: 1.8;\n      color: #4b5563;\n    }\n\n    \/* =========================================================\n       RESPONSIVE\n    ========================================================= *\/\n\n    @media (max-width: 1024px) {\n      .ols-t4-cards-grid {\n        grid-template-columns: repeat(2, minmax(0, 1fr));\n      }\n    }\n\n    @media (max-width: 860px) {\n      .ols-t4-intro-inner {\n        grid-template-columns: 1fr;\n        gap: 40px;\n      }\n    }\n\n    @media (max-width: 640px) {\n      .ols-t4-intro {\n        padding: 24px 0 52px;\n      }\n\n      .ols-t4-topics {\n        padding: 52px 0 58px;\n      }\n\n      .ols-t4-cards-grid {\n        grid-template-columns: 1fr;\n        gap: 14px;\n      }\n\n      .ols-t4-spec-section {\n        padding: 52px 0 64px;\n      }\n\n      .ols-t4-spec-wrap {\n        padding: 24px 18px;\n        border-radius: 20px;\n      }\n\n      .ols-t4-info-grid {\n        grid-template-columns: 1fr 1fr;\n      }\n    }\n\n  <\/style>\n\n  <!-- BREADCRUMB BAR - sits above everything -->\n  <div class=\"ols-t4-breadcrumb-bar\">\n    <div class=\"ols-t4-container\">\n      <nav class=\"ols-t4-breadcrumb\" aria-label=\"Breadcrumb\">\n      <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\">Revision Notes<\/a> \/\n      <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\">A Level Chemistry<\/a> \/\n      <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/\">Edexcel<\/a> \/\n      <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/\">Topic 4 Inorganic Chemistry and The Periodic Table<\/a> \/\n      <span>Group 7 Halogens<\/span>\n    <\/nav>\n    <\/div>\n  <\/div>\n\n  <!-- INTRO -->\n  <section class=\"ols-t4-intro\">\n    <div class=\"ols-t4-container\">\n      <div class=\"ols-t4-intro-inner\">\n        <div>\n          <div class=\"ols-t4-eyebrow\">Edexcel A Level Chemistry<\/div>\n          <h1>Group 7 Halogens<\/h1>\n          <div class=\"ols-t4-accent-bar\"><\/div>\n          <p class=\"ols-t4-intro-lead\">\n            Group 7 is the p-block mirror of Group 2: the same reasoning about size and shielding, but now the halogens gain electrons instead of losing them. These pages cover the physical trends, the halogens as oxidising agents, the disproportionation reactions of chlorine and the halide ions as reducing agents together with their tests.\n          <\/p>\n        <\/div>\n        <div class=\"ols-t4-info-grid\">\n          <div class=\"ols-t4-info-card\"><div class=\"ols-t4-info-card-label\">Exam Papers<\/div><div class=\"ols-t4-info-card-value\">Paper 1<\/div><div class=\"ols-t4-info-card-sub\">9CH0\/01<\/div><\/div>\n          <div class=\"ols-t4-info-card\"><div class=\"ols-t4-info-card-label\">Specification Points<\/div><div class=\"ols-t4-info-card-value\">4.9 &#8211; 4.14<\/div><div class=\"ols-t4-info-card-sub\">6 points covered<\/div><\/div>\n          <div class=\"ols-t4-info-card\"><div class=\"ols-t4-info-card-label\">Sub-topics<\/div><div class=\"ols-t4-info-card-value\">4 lessons<\/div><div class=\"ols-t4-info-card-sub\">Revision notes available<\/div><\/div>\n          <div class=\"ols-t4-info-card\"><div class=\"ols-t4-info-card-label\">Exam Board<\/div><div class=\"ols-t4-info-card-value\">Edexcel<\/div><div class=\"ols-t4-info-card-sub\">Pearson 9CH0<\/div><\/div>\n        <\/div>\n      <\/div>\n    <\/div>\n  <\/section>\n\n  <!-- TOPIC CARDS -->\n  <section class=\"ols-t4-topics\">\n    <div class=\"ols-t4-container\">\n      <div class=\"ols-t4-section-header\">\n        <h2 class=\"ols-t4-section-title\">Revision Notes<\/h2>\n        <p class=\"ols-t4-section-sub\">Work through each part of Edexcel Topic 4 in a structured sequence.<\/p>\n      <\/div>\n      <div class=\"ols-t4-cards-grid\">\n\n        <!-- Card 1: Trends in the Halogens -->\n        <a class=\"ols-t4-card ols-t4-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/trends-in-the-halogens\/\">\n          <div class=\"ols-t4-card-img-wrap\">\n            <div class=\"ols-t4-visual ols-t4-visual--shape\">\n              <div class=\"ols-t4-visual-panel\">\n                  <div class=\"ols-t4-visual-kicker\">F\u2082 to I\u2082<\/div>\n                  <div class=\"ols-t4-visual-main\">Halogen Trends<\/div>\n                  <div class=\"ols-t4-visual-sub\">colour, volatility, electronegativity<\/div>\n                <\/div>\n            <\/div>\n            <div class=\"ols-t4-card-num\">1<\/div>\n          <\/div>\n          <div class=\"ols-t4-card-body\">\n            <p class=\"ols-t4-card-title\">Trends in the Halogens<\/p>\n            <p class=\"ols-t4-card-desc\">The trends in Group 7: states, colours, boiling points, electronegativity, reactivity and predictions for fluorine and astatine.<\/p>\n            <span class=\"ols-t4-card-cta\">\n              Start revising\n              <svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M3 8h10M9 4l4 4-4 4\"><\/path><\/svg>\n            <\/span>\n          <\/div>\n        <\/a>\n\n        <!-- Card 2: Halogens as Oxidising Agents -->\n        <a class=\"ols-t4-card ols-t4-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/halogens-as-oxidising-agents\/\">\n          <div class=\"ols-t4-card-img-wrap\">\n            <div class=\"ols-t4-visual ols-t4-visual--amber\">\n              <div class=\"ols-t4-visual-panel\">\n                  <div class=\"ols-t4-visual-kicker\">Displacement<\/div>\n                  <div class=\"ols-t4-visual-main\">Oxidising Agents<\/div>\n                  <div class=\"ols-t4-visual-sub\">Cl\u2082 > Br\u2082 > I\u2082<\/div>\n                <\/div>\n            <\/div>\n            <div class=\"ols-t4-card-num\">2<\/div>\n          <\/div>\n          <div class=\"ols-t4-card-body\">\n            <p class=\"ols-t4-card-title\">Halogens as Oxidising Agents<\/p>\n            <p class=\"ols-t4-card-desc\">The halogens as oxidising agents: displacement reactions, colours in water and cyclohexane, reactions with metals and hydrogen, and the reactivity trend.<\/p>\n            <span class=\"ols-t4-card-cta\">\n              Start revising\n              <svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M3 8h10M9 4l4 4-4 4\"><\/path><\/svg>\n            <\/span>\n          <\/div>\n        <\/a>\n\n        <!-- Card 3: Disproportionation Reactions of Chlorine -->\n        <a class=\"ols-t4-card ols-t4-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/disproportionation-reactions-of-chlorine\/\">\n          <div class=\"ols-t4-card-img-wrap\">\n            <div class=\"ols-t4-visual ols-t4-visual--teal\">\n              <div class=\"ols-t4-visual-panel\">\n                  <div class=\"ols-t4-visual-kicker\">Water and bleach<\/div>\n                  <div class=\"ols-t4-visual-main\">Chlorine Reactions<\/div>\n                  <div class=\"ols-t4-visual-sub\">Cl\u2082 + H\u2082O, Cl\u2082 + NaOH<\/div>\n                <\/div>\n            <\/div>\n            <div class=\"ols-t4-card-num\">3<\/div>\n          <\/div>\n          <div class=\"ols-t4-card-body\">\n            <p class=\"ols-t4-card-title\">Disproportionation Reactions of Chlorine<\/p>\n            <p class=\"ols-t4-card-desc\">The disproportionation of chlorine with water and with cold and hot alkali, bleach, water treatment and analogous halogen reactions.<\/p>\n            <span class=\"ols-t4-card-cta\">\n              Start revising\n              <svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M3 8h10M9 4l4 4-4 4\"><\/path><\/svg>\n            <\/span>\n          <\/div>\n        <\/a>\n\n        <!-- Card 4: Halide Ions: Reducing Agents and Tests -->\n        <a class=\"ols-t4-card ols-t4-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/halide-ions-reducing-agents-and-tests\/\">\n          <div class=\"ols-t4-card-img-wrap\">\n            <div class=\"ols-t4-visual ols-t4-visual--shape\">\n              <div class=\"ols-t4-visual-panel\">\n                  <div class=\"ols-t4-visual-kicker\">Cl\u207b, Br\u207b, I\u207b<\/div>\n                  <div class=\"ols-t4-visual-main\">Halide Ions<\/div>\n                  <div class=\"ols-t4-visual-sub\">H\u2082SO\u2084, AgNO\u2083, NH\u2083<\/div>\n                <\/div>\n            <\/div>\n            <div class=\"ols-t4-card-num\">4<\/div>\n          <\/div>\n          <div class=\"ols-t4-card-body\">\n            <p class=\"ols-t4-card-title\">Halide Ions: Reducing Agents and Tests<\/p>\n            <p class=\"ols-t4-card-desc\">Halide ions: reducing power with concentrated sulfuric acid, the acidified silver nitrate test and ammonia, and the hydrogen halides with ammonia and water.<\/p>\n            <span class=\"ols-t4-card-cta\">\n              Start revising\n              <svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M3 8h10M9 4l4 4-4 4\"><\/path><\/svg>\n            <\/span>\n          <\/div>\n        <\/a>\n\n      <\/div>\n    <\/div>\n  <\/section>\n\n  <!-- SPECIFICATION SECTION -->\n  <!-- OLS-SMAP -->\n<style>\r\n.ols-smap{--sm-navy:#1C244B;--sm-blue:#467FF7;--sm-teal:#0f8b8d;--sm-muted:#5f6b84;--sm-border:#e3e8f2;margin:44px auto 8px;max-width:1140px;padding:0 20px;font-family:inherit}\r\n.ols-smap-head{display:flex;align-items:baseline;justify-content:space-between;gap:12px;flex-wrap:wrap;margin:0 0 18px}\r\n.ols-smap-head h2{font-size:clamp(22px,2.6vw,28px);font-weight:800;color:var(--sm-navy);margin:0;letter-spacing:-.01em}\r\n.ols-smap-head p{margin:0;color:var(--sm-muted);font-size:14px}\r\n.ols-smap-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(100%,460px),1fr));gap:20px}\r\n.ols-smap-card{display:grid;grid-template-columns:150px 1fr;background:#fff;border:1px solid var(--sm-border);border-radius:22px;overflow:hidden;box-shadow:0 10px 28px rgba(28,36,75,.08);transition:transform .28s cubic-bezier(.34,1.56,.64,1),box-shadow .28s ease,border-color .28s ease}\r\n.ols-smap-card:hover{transform:translateY(-6px);box-shadow:0 24px 48px rgba(28,36,75,.14);border-color:rgba(70,127,247,.35)}\r\n.ols-smap-vis{background:linear-gradient(160deg,#1C244B 0%,#2d3c7a 100%);display:flex;align-items:center;justify-content:center;padding:14px}\r\n.ols-smap-vis svg{width:100%;max-width:118px;height:auto;display:block}\r\n.ols-smap-body{padding:18px 20px 20px;display:flex;flex-direction:column;gap:6px;min-width:0}\r\n.ols-smap-kicker{font-size:11px;font-weight:800;letter-spacing:.08em;text-transform:uppercase;color:var(--sm-teal)}\r\n.ols-smap-title{font-size:17px;font-weight:800;color:var(--sm-navy);margin:0;line-height:1.25}\r\n.ols-smap-board{font-size:12.5px;color:var(--sm-muted);margin:0}\r\n.ols-smap-desc{font-size:14px;color:#33405e;margin:4px 0 0;line-height:1.5}\r\n.ols-smap-row{display:flex;align-items:center;gap:12px;flex-wrap:wrap;margin-top:10px}\r\n.ols-smap-btn{display:inline-flex;align-items:center;gap:8px;background:var(--sm-navy);color:#fff !important;text-decoration:none !important;font-weight:700;font-size:14px;padding:10px 18px;border-radius:999px;transition:background .2s ease,transform .2s ease}\r\n.ols-smap-btn:hover{background:var(--sm-blue);transform:translateY(-1px)}\r\n.ols-smap-btn svg{width:16px;height:16px}\r\n.ols-smap-meta{font-size:12px;color:var(--sm-muted)}\r\n.ols-smap-note{font-size:11.5px;color:var(--sm-muted);margin:14px 0 0;text-align:center}\r\n@media (max-width:560px){.ols-smap{padding:0 16px;margin-top:32px}.ols-smap-card{grid-template-columns:76px 1fr}.ols-smap-vis{padding:8px}.ols-smap-vis svg{max-width:60px}.ols-smap-body{padding:14px 14px 16px}.ols-smap-title{font-size:16px}.ols-smap-desc{font-size:13.5px}.ols-smap-btn{padding:9px 15px;font-size:13.5px}}\r\n<\/style><section class=\"ols-smap\" aria-label=\"Summary map\"><div class=\"ols-smap-head\"><h2>Summary map<\/h2><p>Download, print and revise the key facts of this topic at a glance.<\/p><\/div><div class=\"ols-smap-grid\"><article class=\"ols-smap-card\"><div class=\"ols-smap-vis\"><svg viewBox=\"0 0 120 120\" aria-hidden=\"true\"><g fill=\"none\" stroke=\"#ffffff\" stroke-width=\"2.4\" stroke-linecap=\"round\"><circle cx=\"60\" cy=\"60\" r=\"17\"\/><path d=\"M60 43V20M60 77v23M43 60H20M77 60h23M48 48 32 32M72 48l16-16M48 72 32 88M72 72l16 16\"\/><\/g><g fill=\"#ffffff\"><path d=\"M60 16l-4 7h8zM60 104l-4-7h8zM16 60l7-4v8zM104 60l-7-4v8zM29 29l2.5 7.5 5-5zM91 29l-7.5 2.5 5 5zM29 91l7.5-2.5-5-5zM91 91l-2.5-7.5-5 5z\"\/><\/g><g fill=\"#5fd0c9\"><circle cx=\"60\" cy=\"11\" r=\"3\"\/><circle cx=\"109\" cy=\"60\" r=\"3\"\/><\/g><g fill=\"#f2c14e\"><circle cx=\"11\" cy=\"60\" r=\"3\"\/><circle cx=\"96\" cy=\"96\" r=\"3\"\/><\/g><g fill=\"#9db8ff\"><circle cx=\"24\" cy=\"24\" r=\"3\"\/><circle cx=\"60\" cy=\"109\" r=\"3\"\/><\/g><\/svg><\/div><div class=\"ols-smap-body\"><span class=\"ols-smap-kicker\">Summary map \u00b7 PDF<\/span><p class=\"ols-smap-title\">Halogens Map<\/p><p class=\"ols-smap-board\">Edexcel A Level Chemistry \u00b7 Topic 4 Inorganic Chemistry and the Periodic Table \u00b7 Group 7<\/p><p class=\"ols-smap-desc\">The whole section on one A4 page: physical trends, displacement, halogens with metals, chlorine disproportionating, halides with H\u2082SO\u2084, and halide tests and predictions.<\/p><div class=\"ols-smap-row\"><a class=\"ols-smap-btn\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/ols-maps\/map-dom-4b-halogens.pdf\" download rel=\"nofollow\"><svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M8 2v8M4.5 6.5 8 10l3.5-3.5M3 13h10\"\/><\/svg>Download the map<\/a><span class=\"ols-smap-meta\">6 key ideas + a data table \u00b7 A4 portrait \u00b7 print ready<\/span><\/div><\/div><\/article><\/div><p class=\"ols-smap-note\">\u00a9 2026 Online Learning System. For personal study: printing is allowed; editing, copying and redistribution are not.<\/p><\/section>\n<!-- \/OLS-SMAP -->\n<section class=\"ols-t4-spec-section\">\n    <div class=\"ols-t4-container\">\n      <div class=\"ols-t4-spec-desktop\">\n        <div class=\"ols-t4-spec-wrap\">\n          <div class=\"ols-t4-spec-pill\">Specification Coverage<\/div>\n          <h2 class=\"ols-t4-spec-heading\">Group 7 Halogens &#8211; Edexcel A Level Chemistry<\/h2>\n          <p class=\"ols-t4-spec-intro-text\">The following specification points outline the knowledge and skills students are expected to demonstrate for Topic 4.<\/p>\n<h3 class=\"ols-t4-spec-group-title\">4B: The elements of Group 7, halogens<\/h3>\n<div class=\"ols-t4-spec-rows\">\n<div class=\"ols-t4-spec-row ols-t4-spec-row--light\">\n              <div class=\"ols-t4-spec-code ols-t4-spec-code--dark\">4.9<\/div>\n              <div class=\"ols-t4-spec-text\">understand reasons for the trends in melting and boiling temperatures, physical state at room temperature, and electronegativity for Group 7 elements<\/div>\n            <\/div>\n<div class=\"ols-t4-spec-row ols-t4-spec-row--light\">\n              <div class=\"ols-t4-spec-code ols-t4-spec-code--dark\">4.10<\/div>\n              <div class=\"ols-t4-spec-text\">understand reasons for the trend in reactivity of Group 7 elements down the group<\/div>\n            <\/div>\n<div class=\"ols-t4-spec-row ols-t4-spec-row--light\">\n              <div class=\"ols-t4-spec-code ols-t4-spec-code--dark\">4.11<\/div>\n              <div class=\"ols-t4-spec-text\">understand the trend in reactivity of Group 7 elements in terms of the redox reactions of Cl<sub>2<\/sub>, Br<sub>2<\/sub> and I<sub>2<\/sub> with halide ions in aqueous solution, followed by the addition of an organic solvent<\/div>\n            <\/div>\n<div class=\"ols-t4-spec-row ols-t4-spec-row--mid\">\n              <div class=\"ols-t4-spec-code ols-t4-spec-code--mid\">4.12<\/div>\n              <div class=\"ols-t4-spec-text\">understand, in terms of changes in oxidation number, the following reactions of the halogens:<div class=\"ols-t4-spec-sub-list\"><div class=\"ols-t4-spec-sub-row\"><div class=\"ols-t4-spec-sub-code\">i<\/div><div class=\"ols-t4-spec-sub-text\">oxidation reactions with Group 1 and 2 metals<\/div><\/div><div class=\"ols-t4-spec-sub-row\"><div class=\"ols-t4-spec-sub-code\">ii<\/div><div class=\"ols-t4-spec-sub-text\">the disproportionation reaction of chlorine with water and the use of chlorine in water treatment<\/div><\/div><div class=\"ols-t4-spec-sub-row\"><div class=\"ols-t4-spec-sub-code\">iii<\/div><div class=\"ols-t4-spec-sub-text\">the disproportionation reaction of chlorine with cold, dilute aqueous sodium hydroxide to form bleach<\/div><\/div><div class=\"ols-t4-spec-sub-row\"><div class=\"ols-t4-spec-sub-code\">iv<\/div><div class=\"ols-t4-spec-sub-text\">the disproportionation reaction of chlorine with hot alkali<\/div><\/div><div class=\"ols-t4-spec-sub-row\"><div class=\"ols-t4-spec-sub-code\">v<\/div><div class=\"ols-t4-spec-sub-text\">reactions analogous to those specified above<\/div><\/div><\/div><\/div>\n            <\/div>\n<div class=\"ols-t4-spec-row ols-t4-spec-row--mid\">\n              <div class=\"ols-t4-spec-code ols-t4-spec-code--mid\">4.13<\/div>\n              <div class=\"ols-t4-spec-text\">understand the following reactions:<div class=\"ols-t4-spec-sub-list\"><div class=\"ols-t4-spec-sub-row\"><div class=\"ols-t4-spec-sub-code\">i<\/div><div class=\"ols-t4-spec-sub-text\">solid Group 1 halides with concentrated sulfuric acid, to illustrate the trend in reducing ability of the hydrogen halides<\/div><\/div><div class=\"ols-t4-spec-sub-row\"><div class=\"ols-t4-spec-sub-code\">ii<\/div><div class=\"ols-t4-spec-sub-text\">precipitation reactions of the aqueous anions Cl<sup>&#8211;<\/sup>, Br<sup>&#8211;<\/sup> and I<sup>&#8211;<\/sup> with aqueous silver nitrate solution, followed by aqueous ammonia solution<\/div><\/div><div class=\"ols-t4-spec-sub-row\"><div class=\"ols-t4-spec-sub-code\">iii<\/div><div class=\"ols-t4-spec-sub-text\">hydrogen halides with ammonia and with water, to produce acids<\/div><\/div><\/div><\/div>\n            <\/div>\n<div class=\"ols-t4-spec-row ols-t4-spec-row--light\">\n              <div class=\"ols-t4-spec-code ols-t4-spec-code--dark\">4.14<\/div>\n              <div class=\"ols-t4-spec-text\">be able to make predictions about fluorine and astatine and their compounds, in terms of knowledge of trends in halogen chemistry<\/div>\n            <\/div>\n<\/div>\n        <\/div>\n      <\/div>\n      <div class=\"ols-t4-spec-mobile\">\n        <div class=\"ols-t4-spec-wrap\">\n          <div class=\"ols-t4-spec-pill\">Specification Coverage<\/div>\n          <h2 class=\"ols-t4-spec-heading\">Group 7 Halogens &#8211; Edexcel A Level Chemistry<\/h2>\n          <p class=\"ols-t4-spec-intro-text\">The following specification points outline the knowledge and skills students are expected to demonstrate for Topic 4.<\/p>\n<h3 class=\"ols-t4-spec-group-title\">4B: The elements of Group 7, halogens<\/h3>\n<div class=\"ols-t4-spec-mob-rows\">\n<div class=\"ols-t4-spec-mob-row ols-t4-spec-mob-row--light\">\n              <div class=\"ols-t4-spec-mob-code\">4.9<\/div>\n              <div class=\"ols-t4-spec-mob-text\">understand reasons for the trends in melting and boiling temperatures, physical state at room temperature, and electronegativity for Group 7 elements<\/div>\n            <\/div>\n<div class=\"ols-t4-spec-mob-row ols-t4-spec-mob-row--light\">\n              <div class=\"ols-t4-spec-mob-code\">4.10<\/div>\n              <div class=\"ols-t4-spec-mob-text\">understand reasons for the trend in reactivity of Group 7 elements down the group<\/div>\n            <\/div>\n<div class=\"ols-t4-spec-mob-row ols-t4-spec-mob-row--light\">\n              <div class=\"ols-t4-spec-mob-code\">4.11<\/div>\n              <div class=\"ols-t4-spec-mob-text\">understand the trend in reactivity of Group 7 elements in terms of the redox reactions of Cl<sub>2<\/sub>, Br<sub>2<\/sub> and I<sub>2<\/sub> with halide ions in aqueous solution, followed by the addition of an organic solvent<\/div>\n            <\/div>\n<div class=\"ols-t4-spec-mob-row ols-t4-spec-mob-row--mid\">\n              <div class=\"ols-t4-spec-mob-code ols-t4-spec-mob-code--mid\">4.12<\/div>\n              <div class=\"ols-t4-spec-mob-text\">understand, in terms of changes in oxidation number, the following reactions of the halogens:<div class=\"ols-t4-spec-mob-sub-list\"><div class=\"ols-t4-spec-mob-sub-row\"><div class=\"ols-t4-spec-mob-sub-code\">i<\/div><div class=\"ols-t4-spec-mob-sub-text\">oxidation reactions with Group 1 and 2 metals<\/div><\/div><div class=\"ols-t4-spec-mob-sub-row\"><div class=\"ols-t4-spec-mob-sub-code\">ii<\/div><div class=\"ols-t4-spec-mob-sub-text\">the disproportionation reaction of chlorine with water and the use of chlorine in water treatment<\/div><\/div><div class=\"ols-t4-spec-mob-sub-row\"><div class=\"ols-t4-spec-mob-sub-code\">iii<\/div><div class=\"ols-t4-spec-mob-sub-text\">the disproportionation reaction of chlorine with cold, dilute aqueous sodium hydroxide to form bleach<\/div><\/div><div class=\"ols-t4-spec-mob-sub-row\"><div class=\"ols-t4-spec-mob-sub-code\">iv<\/div><div class=\"ols-t4-spec-mob-sub-text\">the disproportionation reaction of chlorine with hot alkali<\/div><\/div><div class=\"ols-t4-spec-mob-sub-row\"><div class=\"ols-t4-spec-mob-sub-code\">v<\/div><div class=\"ols-t4-spec-mob-sub-text\">reactions analogous to those specified above<\/div><\/div><\/div><\/div>\n            <\/div>\n<div class=\"ols-t4-spec-mob-row ols-t4-spec-mob-row--mid\">\n              <div class=\"ols-t4-spec-mob-code ols-t4-spec-mob-code--mid\">4.13<\/div>\n              <div class=\"ols-t4-spec-mob-text\">understand the following reactions:<div class=\"ols-t4-spec-mob-sub-list\"><div class=\"ols-t4-spec-mob-sub-row\"><div class=\"ols-t4-spec-mob-sub-code\">i<\/div><div class=\"ols-t4-spec-mob-sub-text\">solid Group 1 halides with concentrated sulfuric acid, to illustrate the trend in reducing ability of the hydrogen halides<\/div><\/div><div class=\"ols-t4-spec-mob-sub-row\"><div class=\"ols-t4-spec-mob-sub-code\">ii<\/div><div class=\"ols-t4-spec-mob-sub-text\">precipitation reactions of the aqueous anions Cl<sup>&#8211;<\/sup>, Br<sup>&#8211;<\/sup> and I<sup>&#8211;<\/sup> with aqueous silver nitrate solution, followed by aqueous ammonia solution<\/div><\/div><div class=\"ols-t4-spec-mob-sub-row\"><div class=\"ols-t4-spec-mob-sub-code\">iii<\/div><div class=\"ols-t4-spec-mob-sub-text\">hydrogen halides with ammonia and with water, to produce acids<\/div><\/div><\/div><\/div>\n            <\/div>\n<div class=\"ols-t4-spec-mob-row ols-t4-spec-mob-row--light\">\n              <div class=\"ols-t4-spec-mob-code\">4.14<\/div>\n              <div class=\"ols-t4-spec-mob-text\">be able to make predictions about fluorine and astatine and their compounds, in terms of knowledge of trends in halogen chemistry<\/div>\n            <\/div>\n<\/div>\n        <\/div>\n      <\/div>\n    <\/div>\n  <\/section>\n\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-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/#webpage\",\n      \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/\",\n      \"name\": \"Group 7 Halogens\",\n      \"inLanguage\": \"en-GB\",\n      \"breadcrumb\": {\n        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/#breadcrumb\"\n      }\n    },\n    {\n      \"@type\": \"BreadcrumbList\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/#breadcrumb\",\n      \"itemListElement\": [\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 1,\n          \"name\": \"Revision Notes\",\n          \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\"\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 2,\n          \"name\": \"A Level Chemistry\",\n          \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\"\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 3,\n          \"name\": \"Edexcel\",\n          \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/\"\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 4,\n          \"name\": \"Topic 4 Inorganic Chemistry and The Periodic Table\",\n          \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/\"\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 5,\n          \"name\": \"Group 7 Halogens\",\n          \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/\"\n        }\n      ]\n    },\n    {\n      \"@type\": \"ItemList\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/#pages\",\n      \"name\": \"Group 7 Halogens revision notes\",\n      \"itemListElement\": [\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 1,\n          \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/trends-in-the-halogens\/\",\n          \"name\": \"Trends in the Halogens\"\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 2,\n          \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/halogens-as-oxidising-agents\/\",\n          \"name\": \"Halogens as Oxidising Agents\"\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 3,\n          \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/disproportionation-reactions-of-chlorine\/\",\n          \"name\": \"Disproportionation Reactions of Chlorine\"\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 4,\n          \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/group-7-halogens\/halide-ions-reducing-agents-and-tests\/\",\n          \"name\": \"Halide Ions: Reducing Agents and Tests\"\n        }\n      ]\n    }\n  ]\n}\n<\/script>\n\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Revision Notes \/ A Level Chemistry \/ Edexcel \/ Topic 4 Inorganic Chemistry and The Periodic Table \/ Group 7 Halogens Edexcel A Level Chemistry Group 7 Halogens Group 7 is the p-block mirror of Group 2: the same reasoning about size and shielding, but now the halogens gain electrons instead of losing them. These [&hellip;]<\/p>\n","protected":false},"author":12,"featured_media":0,"parent":4500,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-4682","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/4682","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/comments?post=4682"}],"version-history":[{"count":1,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/4682\/revisions"}],"predecessor-version":[{"id":23792,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/4682\/revisions\/23792"}],"up":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/4500"}],"wp:attachment":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/media?parent=4682"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}