{"id":4499,"date":"2026-05-28T05:24:45","date_gmt":"2026-05-28T04:24:45","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-3-redox-i\/"},"modified":"2026-06-02T07:10:20","modified_gmt":"2026-06-02T06:10:20","slug":"topic-3-redox-i","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-3-redox-i\/","title":{"rendered":"Topic 3 &#8211; Redox I"},"content":{"rendered":"\n<div class=\"ols-t3-page\">\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 3 Redox I<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-3-redox-i\/oxidation-numbers\/\">Oxidation Numbers<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-3-redox-i\/electron-transfer-and-half-equations\/\">Electron Transfer and Half-Equations<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-3-redox-i\/disproportionation\/\">Disproportionation<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-3-redox-i\/redox-classification\/\">Redox Classification<\/a>\r\n      <\/li>\r\n\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Next Topics<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a 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margin-top: 10px;\n    }\n\n    .ols-t3-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-t3-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-t3-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-t3-cards-grid {\n        grid-template-columns: repeat(2, minmax(0, 1fr));\n      }\n    }\n\n    @media (max-width: 860px) {\n      .ols-t3-intro-inner {\n        grid-template-columns: 1fr;\n        gap: 40px;\n      }\n    }\n\n    @media (max-width: 640px) {\n      .ols-t3-intro {\n        padding: 24px 0 52px;\n      }\n\n      .ols-t3-topics {\n        padding: 52px 0 58px;\n      }\n\n      .ols-t3-cards-grid {\n        grid-template-columns: 1fr;\n        gap: 14px;\n      }\n\n      .ols-t3-spec-section {\n        padding: 52px 0 64px;\n      }\n\n      .ols-t3-spec-wrap {\n        padding: 24px 18px;\n        border-radius: 20px;\n      }\n\n      .ols-t3-info-grid {\n        grid-template-columns: 1fr 1fr;\n      }\n    }\n\n  <\/style>\n\n  <!-- BREADCRUMB BAR - sits above everything -->\n  <div class=\"ols-t3-breadcrumb-bar\">\n    <div class=\"ols-t3-container\">\n      <nav class=\"ols-t3-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        <span>Topic 3 Redox I<\/span>\n      <\/nav>\n    <\/div>\n  <\/div>\n\n  <!-- INTRO -->\n  <section class=\"ols-t3-intro\">\n    <div class=\"ols-t3-container\">\n      <div class=\"ols-t3-intro-inner\">\n        <div>\n          <div class=\"ols-t3-eyebrow\">Edexcel A Level Chemistry<\/div>\n          <h1>Topic 3<br>Redox I<\/h1>\n          <div class=\"ols-t3-accent-bar\"><\/div>\n          <p class=\"ols-t3-intro-lead\">Topic 3 introduces oxidation number as a way to classify redox reactions, identify oxidation and reduction, write ionic half-equations and construct full ionic equations. Students build the language needed for redox chemistry across both inorganic and organic contexts.<\/p>\n        <\/div>\n        <div class=\"ols-t3-info-grid\">\n          <div class=\"ols-t3-info-card\"><div class=\"ols-t3-info-card-label\">Exam Papers<\/div><div class=\"ols-t3-info-card-value\">Paper 1 &amp; 2<\/div><div class=\"ols-t3-info-card-sub\">9CH0\/01 and 9CH0\/02<\/div><\/div>\n          <div class=\"ols-t3-info-card\"><div class=\"ols-t3-info-card-label\">Specification Points<\/div><div class=\"ols-t3-info-card-value\">3.1 &#8211; 3.13<\/div><div class=\"ols-t3-info-card-sub\">13 points covered<\/div><\/div>\n          <div class=\"ols-t3-info-card\"><div class=\"ols-t3-info-card-label\">Topic Parts<\/div><div class=\"ols-t3-info-card-value\">4 parts<\/div><div class=\"ols-t3-info-card-sub\">Revision notes available<\/div><\/div>\n          <div class=\"ols-t3-info-card\"><div class=\"ols-t3-info-card-label\">Exam Board<\/div><div class=\"ols-t3-info-card-value\">Edexcel<\/div><div class=\"ols-t3-info-card-sub\">Pearson 9CH0<\/div><\/div>\n        <\/div>\n      <\/div>\n    <\/div>\n  <\/section>\n\n  <!-- TOPIC CARDS -->\n  <section class=\"ols-t3-topics\">\n    <div class=\"ols-t3-container\">\n      <div class=\"ols-t3-section-header\">\n        <h2 class=\"ols-t3-section-title\">Revision Notes<\/h2>\n        <p class=\"ols-t3-section-sub\">Work through each part of Edexcel Topic 3 in a structured sequence.<\/p>\n      <\/div>\n      <div class=\"ols-t3-cards-grid\">\n        <!-- Card 1: Oxidation Numbers -->\n        <a class=\"ols-t3-card ols-t3-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-3-redox-i\/oxidation-numbers\/\">\n          <div class=\"ols-t3-card-img-wrap\">\n            <div class=\"ols-t3-visual ols-t3-visual--amber\">\n              <div class=\"ols-t3-visual-panel\">\n                <div class=\"ols-t3-visual-kicker\">Oxidation state<\/div>\n                <div class=\"ols-t3-visual-main\">Oxidation<br>Numbers<\/div>\n                <div class=\"ols-t3-visual-sub\">+, -, 0 and Roman numerals<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t3-card-num\">1<\/div>\n            <span class=\"ols-t3-card-status ols-t3-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t3-card-body\">\n            <p class=\"ols-t3-card-title\">Oxidation Numbers<\/p>\n            <p class=\"ols-t3-card-desc\">Assigning oxidation numbers in elements, compounds and ions, including Roman numeral notation.<\/p>\n            <span class=\"ols-t3-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        <!-- Card 2: Electron Transfer and Half-Equations -->\n        <a class=\"ols-t3-card ols-t3-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-3-redox-i\/electron-transfer-and-half-equations\/\">\n          <div class=\"ols-t3-card-img-wrap\">\n            <div class=\"ols-t3-visual ols-t3-visual--teal\">\n              <div class=\"ols-t3-visual-panel\">\n                <div class=\"ols-t3-visual-kicker\">Electron flow<\/div>\n                <div class=\"ols-t3-visual-main\">Half<br>Equations<\/div>\n                <div class=\"ols-t3-molecule-row\" aria-hidden=\"true\"><span class=\"ols-t3-ion\">e<sup>&#8211;<\/sup><\/span><span class=\"ols-t3-bond\"><\/span><span class=\"ols-t3-ion\">redox<\/span><\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t3-card-num\">2<\/div>\n            <span class=\"ols-t3-card-status ols-t3-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t3-card-body\">\n            <p class=\"ols-t3-card-title\">Electron Transfer and Half-Equations<\/p>\n            <p class=\"ols-t3-card-desc\">Oxidation, reduction, oxidising agents, reducing agents and constructing ionic half-equations.<\/p>\n            <span class=\"ols-t3-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        <!-- Card 3: Disproportionation -->\n        <a class=\"ols-t3-card ols-t3-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-3-redox-i\/disproportionation\/\">\n          <div class=\"ols-t3-card-img-wrap\">\n            <div class=\"ols-t3-visual ols-t3-visual--rose\">\n              <div class=\"ols-t3-visual-panel\">\n                <div class=\"ols-t3-visual-kicker\">Two changes<\/div>\n                <div class=\"ols-t3-visual-main\">Disproportion<br>ation<\/div>\n                <div class=\"ols-t3-visual-sub\">oxidised and reduced<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t3-card-num\">3<\/div>\n            <span class=\"ols-t3-card-status ols-t3-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t3-card-body\">\n            <p class=\"ols-t3-card-title\">Disproportionation<\/p>\n            <p class=\"ols-t3-card-desc\">Reactions where one element in a single species is oxidised and reduced at the same time.<\/p>\n            <span class=\"ols-t3-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        <!-- Card 4: Redox Classification -->\n        <a class=\"ols-t3-card ols-t3-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-3-redox-i\/redox-classification\/\">\n          <div class=\"ols-t3-card-img-wrap\">\n            <div class=\"ols-t3-visual ols-t3-visual--slate\">\n              <div class=\"ols-t3-visual-panel\">\n                <div class=\"ols-t3-visual-kicker\">Classifying reactions<\/div>\n                <div class=\"ols-t3-visual-main\">Redox<br>Classification<\/div>\n                <div class=\"ols-t3-visual-sub\">identify the chemical change<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t3-card-num\">4<\/div>\n            <span class=\"ols-t3-card-status ols-t3-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t3-card-body\">\n            <p class=\"ols-t3-card-title\">Redox Classification<\/p>\n            <p class=\"ols-t3-card-desc\">Using oxidation numbers and electron transfer to classify reactions as redox or non-redox.<\/p>\n            <span class=\"ols-t3-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      <\/div>\n    <\/div>\n  <\/section>\n\n  <!-- SPECIFICATION SECTION -->\n  <section class=\"ols-t3-spec-section\">\n    <div class=\"ols-t3-container\">\n      <div class=\"ols-t3-spec-desktop\">\n        <div class=\"ols-t3-spec-wrap\">\n          <div class=\"ols-t3-spec-pill\">Specification Coverage<\/div>\n          <h2 class=\"ols-t3-spec-heading\">Topic 3 Redox I &#8211; Edexcel A Level Chemistry<\/h2>\n          <p class=\"ols-t3-spec-intro-text\">The following specification points outline the knowledge and skills students are expected to demonstrate for Topic 3.<\/p>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.1<\/div>\n              <div class=\"ols-t3-spec-text\">know what is meant by the term oxidation number<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.2<\/div>\n              <div class=\"ols-t3-spec-text\">be able to calculate the oxidation number of elements in compounds and ions. The use of oxidation numbers in peroxides and metal hydrides is expected.<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.3<\/div>\n              <div class=\"ols-t3-spec-text\">understand oxidation and reduction in terms of electron transfer and changes in oxidation number, applied to reactions of s- and p-block elements<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.4<\/div>\n              <div class=\"ols-t3-spec-text\">understand oxidation and reduction in terms of electron loss or electron gain<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.5<\/div>\n              <div class=\"ols-t3-spec-text\">know that oxidising agents gain electrons<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.6<\/div>\n              <div class=\"ols-t3-spec-text\">know that reducing agents lose electrons<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.7<\/div>\n              <div class=\"ols-t3-spec-text\">understand that a disproportionation reaction involves an element in a single species being simultaneously oxidised and reduced<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.8<\/div>\n              <div class=\"ols-t3-spec-text\">know that oxidation number is a useful concept in terms of the classification of reactions as redox and as disproportionation<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.9<\/div>\n              <div class=\"ols-t3-spec-text\">be able to indicate the oxidation number of an element in a compound or ion, using a Roman numeral<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.10<\/div>\n              <div class=\"ols-t3-spec-text\">be able to write formulae given oxidation numbers<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.11<\/div>\n              <div class=\"ols-t3-spec-text\">understand that metals, in general, form positive ions by loss of electrons with an increase in oxidation number<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.12<\/div>\n              <div class=\"ols-t3-spec-text\">understand that non-metals, in general, form negative ions by gain of electrons with a decrease in oxidation number<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-row ols-t3-spec-row--light\">\n              <div class=\"ols-t3-spec-code ols-t3-spec-code--dark\">3.13<\/div>\n              <div class=\"ols-t3-spec-text\">be able to write ionic half-equations and use them to construct full ionic equations<\/div>\n            <\/div>\n        <\/div>\n      <\/div>\n      <div class=\"ols-t3-spec-mobile\">\n        <div class=\"ols-t3-spec-wrap\">\n          <div class=\"ols-t3-spec-pill\">Specification Coverage<\/div>\n          <h2 class=\"ols-t3-spec-heading\">Topic 3 Redox I &#8211; Edexcel A Level Chemistry<\/h2>\n          <p class=\"ols-t3-spec-intro-text\">The following specification points outline the knowledge and skills students are expected to demonstrate for Topic 3.<\/p>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.1<\/div>\n              <div class=\"ols-t3-spec-mob-text\">know what is meant by the term oxidation number<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.2<\/div>\n              <div class=\"ols-t3-spec-mob-text\">be able to calculate the oxidation number of elements in compounds and ions. The use of oxidation numbers in peroxides and metal hydrides is expected.<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.3<\/div>\n              <div class=\"ols-t3-spec-mob-text\">understand oxidation and reduction in terms of electron transfer and changes in oxidation number, applied to reactions of s- and p-block elements<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.4<\/div>\n              <div class=\"ols-t3-spec-mob-text\">understand oxidation and reduction in terms of electron loss or electron gain<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.5<\/div>\n              <div class=\"ols-t3-spec-mob-text\">know that oxidising agents gain electrons<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.6<\/div>\n              <div class=\"ols-t3-spec-mob-text\">know that reducing agents lose electrons<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.7<\/div>\n              <div class=\"ols-t3-spec-mob-text\">understand that a disproportionation reaction involves an element in a single species being simultaneously oxidised and reduced<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.8<\/div>\n              <div class=\"ols-t3-spec-mob-text\">know that oxidation number is a useful concept in terms of the classification of reactions as redox and as disproportionation<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.9<\/div>\n              <div class=\"ols-t3-spec-mob-text\">be able to indicate the oxidation number of an element in a compound or ion, using a Roman numeral<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.10<\/div>\n              <div class=\"ols-t3-spec-mob-text\">be able to write formulae given oxidation numbers<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.11<\/div>\n              <div class=\"ols-t3-spec-mob-text\">understand that metals, in general, form positive ions by loss of electrons with an increase in oxidation number<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.12<\/div>\n              <div class=\"ols-t3-spec-mob-text\">understand that non-metals, in general, form negative ions by gain of electrons with a decrease in oxidation number<\/div>\n            <\/div>\n<div class=\"ols-t3-spec-mob-row ols-t3-spec-mob-row--light\">\n              <div class=\"ols-t3-spec-mob-code\">3.13<\/div>\n              <div class=\"ols-t3-spec-mob-text\">be able to write ionic half-equations and use them to construct full ionic equations<\/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-3-redox-i\/\",\n      \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-3-redox-i\/\",\n      \"name\": \"Topic 3 Redox I - Edexcel A Level Chemistry\",\n      \"description\": \"Topic 3 introduces oxidation number as a way to classify redox reactions, identify oxidation and reduction, write ionic half-equations and construct full ionic equations. 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