{"id":3519,"date":"2026-05-14T08:04:16","date_gmt":"2026-05-14T07:04:16","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/?page_id=3519"},"modified":"2026-06-28T05:54:27","modified_gmt":"2026-06-28T04:54:27","slug":"aldehyde","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/aldehyde\/","title":{"rendered":"Aldehyde"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-aldehyde-page\">\n  <style>\n    .ols-revision-page {\n      --navy: #1C244B;\n      --blue: #2563eb;\n      --soft-blue: #eef4ff;\n      --soft-red: #fff7f7;\n      --soft-purple: #f7f0ff;\n      --soft-green: #f0f7f1;\n      --soft-orange: #fff7ed;\n      --grey-text: #667085;\n      --body-text: #1f2937;\n      --border: rgba(28, 36, 75, 0.14);\n      --shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      --inner-shadow: 0 10px 26px rgba(28, 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.ols-table thead { display: none; }\n      .ols-table tr { margin-bottom: 14px; border: 1px solid var(--border); border-radius: 18px; overflow: hidden; background: #ffffff; box-shadow: var(--inner-shadow); }\n      .ols-table td { border-bottom: 1px solid var(--border); padding: 14px 16px; overflow-wrap: anywhere; }\n      .ols-table td:last-child { border-bottom: none; }\n      .ols-table td::before { content: attr(data-label); display: block; margin-bottom: 6px; font-size: 13px; font-weight: 700; color: var(--blue); }\n    }\n  <\/style>\n\n  <aside class=\"ols-sidebar\">\r\n  <div class=\"ols-sidebar-header\">\r\n    <h3>Revision Notes<\/h3>\r\n    <p>A Level Chemistry<\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Topic 4 Organic Chemistry &amp; Alkanes<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/hazard-and-risk\/\">Hazard &amp; Risk<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/\">Introduction To Organic Chemistry<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/iupac-rules\/\">IUPAC Rules<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/alkene\/\">Alkene<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/alcohol\/\">Alcohol<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/halogenoalkanes\/\">Halogenoalkanes<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/aldehyde\/\">Aldehyde<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/ketone\/\">Ketone<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/carboxylic-acid\/\">Carboxylic Acid<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/ester\/\">Ester<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/isomerism\/\">Isomerism<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/crude-oil\/\">Alkanes from Crude Oil<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/crude-oil\/fractional-distillation\/\">Fractional Distillation<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/crude-oil\/cracking\/\">Cracking<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/crude-oil\/reforming\/\">Reforming<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/fuel\/\">Alkanes as Fuel<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/fuel\/combustion\/\">Combustion<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/fuel\/oxides-of-sulfur\/\">Oxides of Sulfur<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/fuel\/oxides-of-nitrogen\/\">Oxides of Nitrogen<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/fuel\/catalytic-converter\/\">Catalytic Converter<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/alternative-fuel\/\">Alternative Fuel<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/\">Reactions of Alkanes<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/free-radical-substitution\/\">Free Radical Substitution<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/initiation\/\">Initiation<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/propagation\/\">Propagation<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/termination\/\">Termination<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/further-substitution\/\">Further Substitution<\/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>Next Topics<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-5-alkenes\/\">Alkenes<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-6-energetics\/\">Energetics<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-7-intermolecular-forces\/\">Intermolecular Forces<\/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, 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href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/\">Topic 4 Organic Chemistry &amp; Alkanes<\/a> \/\n        <span>Aldehyde<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Aldehyde<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to aldehyde functional groups, the -al suffix, formyl- prefix, terminal carbonyl groups, dialdehyde naming and priority over alcohols in IUPAC names.<\/p>\n\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Exam board: Edexcel International<\/div>\n          <div class=\"ols-badge\">Topic 4: Organic Chemistry &amp; Alkanes<\/div>\n          <div class=\"ols-badge\">Level: A Level Chemistry<\/div>\n        <\/div>\n        <div class=\"ols-author\">\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            <h2 class=\"ols-author-title\">Written by: Dr. Mohammed Al-Fatah<\/h2>\n            <p class=\"ols-author-description\">Chemistry specialist revision notes for A Level Chemistry.<\/p>\n\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          <\/div>\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 Is an Aldehyde?<\/h2>\n        <\/div>\n\n        <p>An <strong>aldehyde<\/strong> is an organic compound containing the <strong>-CHO<\/strong> functional group. This group contains a <strong>carbonyl group<\/strong>, written as <strong>C=O<\/strong>, with the carbonyl carbon also bonded to a hydrogen atom.<\/p>\n        <p>The aldehyde functional group must occur at the <strong>end of a carbon chain<\/strong>. This is because the carbonyl carbon in an aldehyde is bonded to one hydrogen atom and only one carbon atom from the rest of the molecule.<\/p>\n        <p>The carbonyl carbon is automatically treated as <strong>carbon 1<\/strong>, so a position number is normally not needed for a simple aldehyde suffix.<\/p>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Key idea:<\/strong> An aldehyde contains a terminal -CHO group. The carbonyl carbon is automatically numbered as carbon 1.<\/p>\n        <\/div>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/aldehyde-functional-group.svg\" alt=\"General aldehyde functional group showing a terminal carbonyl group bonded to hydrogen\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>The aldehyde functional group is terminal because the carbonyl carbon is bonded to a hydrogen atom and the rest of the carbon chain.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">2<\/div>\n          <h2>Naming Aldehydes Using the -al Suffix<\/h2>\n        <\/div>\n\n        <p>The name of an aldehyde usually ends in the suffix <strong>-al<\/strong>. The final <strong>-e<\/strong> of the parent alkane is removed before adding <strong>-al<\/strong>.<\/p>\n        <p>For example, <strong>ethane<\/strong> becomes <strong>ethanal<\/strong>. The aldehyde carbon is automatically carbon 1, so the name does not need to be written as ethan-1-al.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Homologous series<\/th>\n                <th>Functional group<\/th>\n                <th>Prefix<\/th>\n                <th>Suffix<\/th>\n                <th>Example<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Homologous series\">Aldehydes<\/td>\n                <td data-label=\"Functional group\">-CHO<\/td>\n                <td data-label=\"Prefix\">formyl-<\/td>\n                <td data-label=\"Suffix\">-al<\/td>\n                <td data-label=\"Example\">ethanal<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-image-grid\">\n          <div class=\"ols-mini-figure\">\n            <div class=\"ols-mini-figure-image\">\n              <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/ethanal.svg\" alt=\"Displayed formula of ethanal showing the aldehyde group\">\n            <\/div>\n            <div class=\"ols-mini-figure-caption\">\n              <p>Ethanal has two carbon atoms and a terminal -CHO group, so its name uses eth- and the aldehyde suffix -al.<\/p>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-mini-figure\">\n            <div class=\"ols-mini-figure-image\">\n              <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/ethanal-skeletal.svg\" alt=\"Skeletal formula of ethanal\">\n            <\/div>\n            <div class=\"ols-mini-figure-caption\">\n              <p>In skeletal formulae, the carbonyl group is shown at the end of the chain to show that the compound is an aldehyde.<\/p>\n            <\/div>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">3<\/div>\n          <h2>Why Aldehydes Do Not Usually Need Position Numbers<\/h2>\n        <\/div>\n\n        <p>For most aldehydes, the <strong>C=O group is on the first carbon<\/strong> of the carbon chain. This means the position of the aldehyde group is fixed by the functional group itself.<\/p>\n        <p>Because the carbonyl carbon is automatically numbered as carbon 1, a simple aldehyde name uses <strong>-al<\/strong> without a location number for the suffix.<\/p>\n\n        <div class=\"ols-rule-list\">\n          <div class=\"ols-rule-item\">\n            <h3>Identify the longest chain containing -CHO<\/h3>\n            <p>Include the carbonyl carbon of the aldehyde group as part of the parent chain.<\/p>\n          <\/div>\n          <div class=\"ols-rule-item\">\n            <h3>Number from the aldehyde carbon<\/h3>\n            <p>The aldehyde carbonyl carbon is carbon 1, so substituents are numbered from this end.<\/p>\n          <\/div>\n          <div class=\"ols-rule-item\">\n            <h3>Add the -al suffix<\/h3>\n            <p>Replace the final -e of the parent alkane name with <strong>-al<\/strong>, such as ethane to ethanal.<\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Exam focus:<\/strong> Do not place the aldehyde group in the middle of the chain. A terminal C=O group with an attached hydrogen is what makes the compound an aldehyde.<\/p>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card orange\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">4<\/div>\n          <h2>Molecules with Two Aldehyde Groups<\/h2>\n        <\/div>\n\n        <p>If a molecule contains <strong>two aldehyde groups<\/strong>, the suffix includes <strong>di<\/strong> before <strong>-al<\/strong>. The parent alkane name keeps the final <strong>e<\/strong> before the dial suffix.<\/p>\n        <p>For example, a four-carbon chain with aldehyde groups at both ends is named as <strong>butanedial<\/strong>. In some teaching resources, you may see the simplified label <strong>butandial<\/strong>, but the key naming idea is that two aldehyde groups are shown using the dial ending.<\/p>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/butandial.svg\" alt=\"Structure of butanedial with aldehyde groups at both ends of the carbon chain\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>Two terminal aldehyde groups are indicated by the dial ending, with one -CHO group at each end of the carbon chain.<\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Number of aldehyde groups<\/th>\n                <th>Name ending<\/th>\n                <th>Meaning<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Number of aldehyde groups\">One<\/td>\n                <td data-label=\"Name ending\">-al<\/td>\n                <td data-label=\"Meaning\">One terminal -CHO group is present.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Number of aldehyde groups\">Two<\/td>\n                <td data-label=\"Name ending\">-dial<\/td>\n                <td data-label=\"Meaning\">Two terminal -CHO groups are present.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">5<\/div>\n          <h2>Aldehydes Have Higher Priority Than Alcohols<\/h2>\n        <\/div>\n\n        <p>Aldehydes have a <strong>higher priority than alcohols<\/strong> in IUPAC naming. If a molecule contains both an aldehyde group and an -OH group, the aldehyde normally provides the main suffix <strong>-al<\/strong>.<\/p>\n        <p>The alcohol group is then named as a substituent using the prefix <strong>hydroxy-<\/strong>, rather than using the alcohol suffix <strong>-ol<\/strong>.<\/p>\n        <p>For example, <strong>4-hydroxybutanal<\/strong> contains an aldehyde group at carbon 1 and an -OH group on carbon 4.<\/p>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/4-hydroxybutanal.svg\" alt=\"Skeletal formula of 4-hydroxybutanal showing an aldehyde group and a hydroxy group\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>The aldehyde group controls the suffix, while the -OH group is named using the hydroxy- prefix because it has lower naming priority here.<\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Remember:<\/strong> If -CHO and -OH are both present, use <strong>-al<\/strong> for the aldehyde and <strong>hydroxy-<\/strong> for the alcohol group.<\/p>\n        <\/div>\n      <\/article>\n\n      <section class=\"ols-h5p-card\">\n        <h2>Check Your Understanding<\/h2>\n        <p>Use these short activities to check aldehyde functional groups, the -al suffix, dialdehyde naming and functional group priority before moving on.<\/p>\n\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-80\" class=\"h5p-iframe\" data-content-id=\"80\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T4.2.5.1 Drag: Aldehyde Key Concepts\"><\/iframe><\/div><\/div>\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-81\" class=\"h5p-iframe\" data-content-id=\"81\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T4.2.5.2 MCQ: Aldehyde Functional Group\"><\/iframe><\/div><\/div>\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-82\" class=\"h5p-iframe\" data-content-id=\"82\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T4.2.5.3 MCQ: Aldehyde Naming and Carbon Numbering\"><\/iframe><\/div><\/div>\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-83\" class=\"h5p-iframe\" data-content-id=\"83\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T4.2.5.4 MCQ: Dialdehydes and Functional Group Priority\"><\/iframe><\/div><\/div>\n      <\/section>\n\n      <section class=\"ols-course-cta-alkenes\" id=\"olsCourseCtaAlkenes001\">\n        <style>\n          .ols-course-cta-alkenes,\n          .ols-course-cta-alkenes * {\n            box-sizing: border-box;\n          }\n\n      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class=\"ols-course-cta-top\">\n\n            <a class=\"ols-course-cta-image-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/organic-chemistry-alkanes-topic-4ab-edexcel-international\/\" aria-label=\"Open the Edexcel International A Level Chemistry Topic 4A\/B Organic Chemistry and Alkanes course page\">\n\n              <div class=\"ols-course-cta-image\">\n                <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/04\/edexcel-international-a-level-chemistry-topic-4a-4b-organic-chemistry-alkanes-course-banner.jpg\" alt=\"Edexcel International A Level Chemistry Topic 4A\/B Organic Chemistry and Alkanes course banner\">\n              <\/div>\n\n            <\/a>\n\n            <div class=\"ols-course-cta-content\">\n\n              <div class=\"ols-course-cta-header-row\">\n\n                <div class=\"ols-course-cta-kicker\">\n                  Complete Topic 4A\/B Organic Chemistry &amp; Alkanes Course\n                <\/div>\n\n                <a class=\"ols-course-button ols-course-button-top\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/organic-chemistry-alkanes-topic-4ab-edexcel-international\/\">\n                  View Course\n                <\/a>\n\n              <\/div>\n\n              <h2>\n                Master Organic Chemistry and Alkanes for Edexcel International A Level Chemistry\n              <\/h2>\n\n            <\/div>\n\n          <\/div>\n\n          <div class=\"ols-course-cta-intro-stats\">\n\n            <p class=\"ols-course-cta-intro\">\n              Continue from these free revision notes into the full Topic 4A\/B Organic Chemistry and Alkanes course, with guided video teaching, diagnostic MCQ practice, teacher-marked short-answer questions and a specification assignment with a personalised progress report.\n            <\/p>\n\n            <div class=\"ols-course-cta-stats\">\n\n              <div class=\"ols-course-stat\">\n                <span>Guided learning<\/span>\n                <strong>16 hours<\/strong>\n              <\/div>\n\n              <div class=\"ols-course-stat\">\n                <span>Video lessons<\/span>\n                <strong>430 mins<\/strong>\n              <\/div>\n\n              <div class=\"ols-course-stat\">\n                <span>MCQ practice<\/span>\n                <strong>73 marks<\/strong>\n              <\/div>\n\n              <div class=\"ols-course-stat\">\n                <span>SAQ practice<\/span>\n                <strong>30 marks<\/strong>\n              <\/div>\n\n            <\/div>\n\n          <\/div>\n\n          <div class=\"ols-course-cta-features\">\n\n            <div class=\"ols-course-feature\">\n              <h3>Guided video teaching<\/h3>\n              <p>\n                Learn the chemistry and exam technique through structured video lessons with worked examples and walkthroughs.\n              <\/p>\n            <\/div>\n\n            <div 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<\/section>\n\n        <section id=\"sceneMcq\" class=\"ols-scene\">\n          <div class=\"ols-mcq-stage\">\n            <div id=\"mcqIntroScreen\" class=\"ols-mcq-intro-screen\">\n              <div class=\"ols-mcq-intro-title-wrap\">\n                <h1 class=\"ols-mcq-intro-title\">\n                  <span id=\"mcqIntroTitleText\"><\/span><span id=\"mcqIntroTitleCursor\" class=\"ols-title-cursor\"><\/span>\n                <\/h1>\n              <\/div>\n            <\/div>\n\n            <div class=\"ols-mcq-scale-wrap\">\n              <main id=\"mcqScreen\" class=\"ols-mcq-screen\">\n                <section class=\"mcq-question-area\">\n                  <p class=\"mcq-question-lead\">Some ionic radii are shown.<\/p>\n\n                  <table class=\"mcq-ionic-table\">\n                    <thead>\n                      <tr>\n                        <th>Ion<\/th>\n                        <th>Ionic radius \/ nm<\/th>\n                      <\/tr>\n                    <\/thead>\n                    <tbody>\n                      <tr><td>Na<sup>+<\/sup><\/td><td>0.102<\/td><\/tr>\n                      <tr><td>K<sup>+<\/sup><\/td><td>0.138<\/td><\/tr>\n                      <tr><td>F<sup>\u2212<\/sup><\/td><td>0.133<\/td><\/tr>\n                      <tr><td>Cl<sup>\u2212<\/sup><\/td><td>0.180<\/td><\/tr>\n                    <\/tbody>\n                  <\/table>\n\n                  <p class=\"mcq-question-main\">Which compound has the strongest ionic bonding?<\/p>\n\n                  <div class=\"mcq-options-wrap\">\n                    <div id=\"mcqWrongOption\" class=\"mcq-option-row\">\n                      <span class=\"mcq-radio\"><\/span>\n                      <span class=\"mcq-radio-ripple\"><\/span>\n                      <span class=\"mcq-option-label\">sodium chloride<\/span>\n\n                      <span id=\"mcqSpecificFeedback\" class=\"mcq-specific-feedback\">\n                        <span id=\"mcqCrossIcon\" class=\"mcq-cross-icon\">\u00d7<\/span>\n                        <span class=\"mcq-specific-feedback-text\">\n                          <span id=\"mcqSpecificText\"><\/span><span id=\"mcqSpecificCursor\" class=\"cursor mcq-specific-cursor\" style=\"display:none;\"><\/span>\n                        <\/span>\n                      <\/span>\n                    <\/div>\n\n                    <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">potassium chloride<\/span><\/div>\n                    <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">sodium fluoride<\/span><\/div>\n                    <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">potassium fluoride<\/span><\/div>\n                  <\/div>\n\n                  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id=\"saqScreen\" class=\"ols-saq-screen\">\n                <section class=\"saq-question-area\">\n                  <div class=\"saq-question-text\">\n                    <strong>(ii)<\/strong>&nbsp;&nbsp; Melting temperature depends on the strength of metallic bonding.<br>\n                    Explain why the metallic bonding in magnesium is much stronger than that in sodium.\n                  <\/div>\n\n                  <div class=\"saq-student-box\">\n                    <span id=\"saqStudentText\"><\/span><span id=\"saqStudentCursor\" class=\"cursor\"><\/span>\n                  <\/div>\n                <\/section>\n\n                <section id=\"saqTeacherFeedback\" class=\"saq-teacher-feedback\">\n                  <span id=\"saqTeacherText\"><\/span><span id=\"saqTeacherCursor\" class=\"cursor saq-teacher-cursor\" style=\"display:none;\"><\/span>\n                <\/section>\n              <\/main>\n            <\/div>\n          <\/div>\n        <\/section>\n\n      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Melting temperature is a result of bonding strength, not the cause of it.\\n\\n\"+\n      \"In metallic bonding, positive metal ions are attracted to a sea of delocalised electrons. The strength of this attraction depends on the charge of the ions and the number of delocalised electrons.\\n\\n\"+\n      \"Magnesium forms Mg\u00b2\u207a ions and contributes two delocalised electrons per atom, whereas sodium forms Na\u207a ions and contributes only one electron. This results in a stronger electrostatic attraction in magnesium. Additionally, Mg\u00b2\u207a ions have a higher charge density than Na\u207a ions, further strengthening the metallic bonding.\\n\\n\"+\n      \"Next time, include:\\n\"+\n      \"\u2022 Ion charge: magnesium forms Mg\u00b2\u207a, sodium forms Na\u207a \u2713\\n\"+\n      \"\u2022 Delocalised electrons: magnesium provides more electrons to the sea \u2713\\n\"+\n      \"\u2022 Charge density: smaller, more highly charged ions create stronger attraction \u2713\\n\\n\"+\n      \"You were close. 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ketones.<\/p>\n\n        <div class=\"ols-related-grid\">\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">IUPAC Rules<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Alcohol<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Ketone<\/a>\n        <\/div>\n      <\/section>\n\n      <!-- OLS Author Copyright Footprint \/ Attribution Card -->\n      <section class=\"ols-attribution-card\">\n        <style>\n          .ols-attribution-card {\n            background: linear-gradient(135deg, #ffffff, #f8fbff);\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            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