{"id":7901,"date":"2026-09-14T21:37:06","date_gmt":"2026-09-14T20:37:06","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/ocr-a\/2-2-1-electron-structure\/"},"modified":"2026-09-14T21:41:33","modified_gmt":"2026-09-14T20:41:33","slug":"2-2-1-electron-structure","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/ocr-a\/2-2-1-electron-structure\/","title":{"rendered":"2.2.1 Electron Structure"},"content":{"rendered":"\n<div class=\"ols-ocr221-page\">\n\n  <aside class=\"ols-sidebar\">\n  <div class=\"ols-sidebar-header\">\n    <h3>Revision Notes<\/h3>\n    <p>OCR A Level Chemistry A<\/p>\n  <\/div>\n  <div class=\"ols-topic-group\">\n    <h4>2.2.1 Electron Structure<\/h4>\n    <ul class=\"ols-topic-list\">\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/ocr-a\/2-2-1-electron-structure\/\">Section overview<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/ocr-a\/2-2-1-electron-structure\/electron-configuration\/\">Electron Configuration<\/a><\/li>\n    <\/ul>\n  <\/div>\n  <div class=\"ols-topic-group\">\n    <h4>Other OCR Sections<\/h4>\n    <ul class=\"ols-topic-list\">\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/ocr-a\/2-1-1-atomic-structure-and-isotopes\/\">2.1.1 Atomic Structure and Isotopes<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/ocr-a\/2-2-2-bonding-and-structure\/\">2.2.2 Bonding and Structure<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/ocr-a\/3-1-1-periodicity\/\">3.1.1 Periodicity<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/ocr-a\/4-1-1-basic-concepts-of-organic-chemistry\/\">4.1.1 Basic Concepts of Organic Chemistry<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/ocr-a\/4-1-2-alkanes\/\">4.1.2 Alkanes<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/ocr-a\/4-1-3-alkenes\/\">4.1.3 Alkenes<\/a><\/li>\n    <\/ul>\n  <\/div>\n<\/aside>\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 = 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(max-width: 640px) {\n      .ols-ocr221-intro { padding: 24px 0 52px; }\n      .ols-ocr221-topics { padding: 52px 0 58px; }\n      .ols-ocr221-cards-grid { grid-template-columns: 1fr; gap: 14px; }\n      .ols-ocr221-spec-section { padding: 52px 0 64px; }\n      .ols-ocr221-spec-wrap { padding: 24px 18px; border-radius: 20px; }\n      .ols-ocr221-info-grid { grid-template-columns: 1fr 1fr; }\n      .ols-ocr221-spec-row { flex-direction: column; }\n      .ols-ocr221-spec-code { flex: 0 0 auto; min-height: 34px; }\n    }\n  <\/style>\n\n  <!-- BREADCRUMB BAR -->\n  <div class=\"ols-ocr221-breadcrumb-bar\">\n    <div class=\"ols-ocr221-container\">\n      <nav class=\"ols-ocr221-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\/ocr-a\/\">OCR<\/a> \/\n        <span>2.2.1 Electron Structure<\/span>\n      <\/nav>\n    <\/div>\n  <\/div>\n\n  <!-- INTRO -->\n  <section class=\"ols-ocr221-intro\">\n    <div class=\"ols-ocr221-container\">\n      <div class=\"ols-ocr221-intro-inner\">\n        <div>\n          <div class=\"ols-ocr221-eyebrow\">OCR A Level Chemistry A &#8211; Module 2 Foundations in Chemistry<\/div>\n          <h1>2.2.1<br>Electron Structure<\/h1>\n          <div class=\"ols-ocr221-accent-bar\"><\/div>\n          <p class=\"ols-ocr221-intro-lead\">Section 2.2.1 covers the electron shells, sub-shells and orbitals, the shapes of s and p orbitals, the filling rules and the electron configurations of atoms and ions up to krypton. One page covers the whole section.<\/p>\n        <\/div>\n        <div class=\"ols-ocr221-info-grid\">\n          <div class=\"ols-ocr221-info-card\"><div class=\"ols-ocr221-info-card-label\">Exam Paper<\/div><div class=\"ols-ocr221-info-card-value\">Paper 1 &amp; 2<\/div><div class=\"ols-ocr221-info-card-sub\">H432\/01 and H432\/02<\/div><\/div>\n          <div class=\"ols-ocr221-info-card\"><div class=\"ols-ocr221-info-card-label\">Specification Points<\/div><div class=\"ols-ocr221-info-card-value\">2.2.1 (a) &#8211; (d)<\/div><div class=\"ols-ocr221-info-card-sub\">4 learning outcomes<\/div><\/div>\n          <div class=\"ols-ocr221-info-card\"><div class=\"ols-ocr221-info-card-label\">Topic Parts<\/div><div class=\"ols-ocr221-info-card-value\">1 of 1 live<\/div><div class=\"ols-ocr221-info-card-sub\">Electron Configuration<\/div><\/div>\n          <div class=\"ols-ocr221-info-card\"><div class=\"ols-ocr221-info-card-label\">Exam Board<\/div><div class=\"ols-ocr221-info-card-value\">OCR A<\/div><div class=\"ols-ocr221-info-card-sub\">H432 (2015 onwards)<\/div><\/div>\n        <\/div>\n      <\/div>\n    <\/div>\n  <\/section>\n\n  <!-- TOPIC CARDS -->\n  <section class=\"ols-ocr221-topics\">\n    <div class=\"ols-ocr221-container\">\n      <div class=\"ols-ocr221-section-header\">\n        <h2 class=\"ols-ocr221-section-title\">Revision Notes<\/h2>\n        <p class=\"ols-ocr221-section-sub\">One page covers section 2.2.1.<\/p>\n      <\/div>\n      <div class=\"ols-ocr221-cards-grid\">\n        <!-- Card 1: Electron Configuration -->\n        <a class=\"ols-ocr221-card ols-ocr221-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/ocr-a\/2-2-1-electron-structure\/electron-configuration\/\">\n          <div class=\"ols-ocr221-card-img-wrap\">\n            <div class=\"ols-ocr221-visual ols-ocr221-visual--shapes\">\n              <div class=\"ols-ocr221-visual-panel\">\n                <div class=\"ols-ocr221-visual-kicker\">Orbitals<\/div>\n                <div class=\"ols-ocr221-visual-main\">Electron<br>Configuration<\/div>\n                <div class=\"ols-ocr221-config-line\" aria-hidden=\"true\"><span>1s\u00b2 2s\u00b2 2p\u2076<\/span><\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-ocr221-card-num\">1<\/div>\n          <\/div>\n          <div class=\"ols-ocr221-card-body\">\n            <p class=\"ols-ocr221-card-title\">Electron Configuration<\/p>\n            <p class=\"ols-ocr221-card-desc\">Shells, sub-shells and orbitals, s and p orbital shapes, filling order and the s p d configurations of atoms and ions up to Z = 36 (2.2.1 (a) to (d)).<\/p>\n            <span class=\"ols-ocr221-card-cta\">Start revising<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><\/span>\n          <\/div>\n        <\/a>\n      <\/div>\n    <\/div>\n  <\/section>\n  <!-- SPECIFICATION -->\n  <section class=\"ols-ocr221-spec-section\">\n    <div class=\"ols-ocr221-container\">\n      <div class=\"ols-ocr221-spec-wrap\">\n        <div class=\"ols-ocr221-spec-pill\">Specification Coverage<\/div>\n        <h2 class=\"ols-ocr221-spec-heading\">2.2.1 Electron Structure &#8211; OCR A Level Chemistry A<\/h2>\n        <p class=\"ols-ocr221-spec-intro-text\">The following OCR A learning outcomes state what candidates should be able to do. Wording is taken from the OCR A Level Chemistry A (H432) specification.<\/p>\n        <h3 class=\"ols-ocr221-spec-group-title\">2.2.1 Electron Structure<\/h3>\n        <div class=\"ols-ocr221-spec-rows\">\n          <div class=\"ols-ocr221-spec-row ols-ocr221-spec-row--light\">\n<div class=\"ols-ocr221-spec-code\">2.2.1(a)<\/div>\n<div class=\"ols-ocr221-spec-text\"><strong>Electron shells<\/strong><div class=\"ols-ocr221-spec-sub-list\"><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">i<\/div><div class=\"ols-ocr221-spec-sub-text\">the number of electrons that can fill the first shell<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">ii<\/div><div class=\"ols-ocr221-spec-sub-text\">the number of electrons that can fill the second shell<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">iii<\/div><div class=\"ols-ocr221-spec-sub-text\">the number of electrons that can fill the third shell<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">iv<\/div><div class=\"ols-ocr221-spec-sub-text\">the number of electrons that can fill the fourth shell<\/div><\/div><\/div><\/div>\n<\/div>\n          <div class=\"ols-ocr221-spec-row ols-ocr221-spec-row--mid\">\n<div class=\"ols-ocr221-spec-code ols-ocr221-spec-code--mid\">2.2.1(b)<\/div>\n<div class=\"ols-ocr221-spec-text\"><strong>Atomic orbitals and sub-shells<\/strong><div class=\"ols-ocr221-spec-sub-list\"><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">i<\/div><div class=\"ols-ocr221-spec-sub-text\">atomic orbitals as a region around the nucleus that can hold up to two electrons, with opposite spins<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">ii)-a<\/div><div class=\"ols-ocr221-spec-sub-text\">the shape of s-orbitals<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">ii)-b<\/div><div class=\"ols-ocr221-spec-sub-text\">the shape of p-orbitals<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">iii)-a<\/div><div class=\"ols-ocr221-spec-sub-text\">the number of orbitals making up s-sub-shells<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">iii)-b<\/div><div class=\"ols-ocr221-spec-sub-text\">the number of orbitals making up p-sub-shells<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">iii)-c<\/div><div class=\"ols-ocr221-spec-sub-text\">the number of orbitals making up d-sub-shells<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">iii)-d<\/div><div class=\"ols-ocr221-spec-sub-text\">the number of electrons that can fill s-sub-shells<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">iii)-e<\/div><div class=\"ols-ocr221-spec-sub-text\">the number of electrons that can fill p-sub-shells<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">iii)-f<\/div><div class=\"ols-ocr221-spec-sub-text\">the number of electrons that can fill d-sub-shells<\/div><\/div><\/div><\/div>\n<\/div>\n          <div class=\"ols-ocr221-spec-row ols-ocr221-spec-row--light\">\n<div class=\"ols-ocr221-spec-code\">2.2.1(c)<\/div>\n<div class=\"ols-ocr221-spec-text\"><strong>Filling of orbitals<\/strong><div class=\"ols-ocr221-spec-sub-list\"><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">i<\/div><div class=\"ols-ocr221-spec-sub-text\">filling of orbitals for the first three shells and the 4s and 4p orbitals in order of increasing energy<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">ii<\/div><div class=\"ols-ocr221-spec-sub-text\">filling of orbitals with the same energy, occupation singly before pairing<\/div><\/div><\/div><\/div>\n<\/div>\n          <div class=\"ols-ocr221-spec-row ols-ocr221-spec-row--mid\">\n<div class=\"ols-ocr221-spec-code ols-ocr221-spec-code--mid\">2.2.1(d)<\/div>\n<div class=\"ols-ocr221-spec-text\"><strong>Electron configurations<\/strong><div class=\"ols-ocr221-spec-sub-list\"><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">i<\/div><div class=\"ols-ocr221-spec-sub-text\">deduction of the electron configurations of atoms, given the atomic number, up to Z = 36<\/div><\/div><div class=\"ols-ocr221-spec-sub-row\"><div class=\"ols-ocr221-spec-sub-code\">ii<\/div><div class=\"ols-ocr221-spec-sub-text\">deduction of the electron configurations of ions, given the atomic number and ionic charge, limited to s- and p-blocks up to Z = 36<\/div><\/div><\/div><\/div>\n<\/div>\n        <\/div>\n      <\/div>\n    <\/div>\n  <\/section>\n  <script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  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