https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/v/compounds-and-chemical-formulas 2025-01-16T17:32:17.772857468Z Compounds and chemical formulas Some substances, like copper or gold, are pure elements. Others, like water (H₂O), are compounds—made from two or more elements in fixed ratios, chemically bonded. Each compound has a unique formula, like CO₂ for carbon dioxide, representing its specific atomic arrangement. Compounds form molecules, tightly bonded units, creating an incredible diversity of substances in nature. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/e3e4181e-5236-462c-82b7-64099d59b95c_1280_720_base.png Compounds and chemical formulas Some substances, like copper or gold, are pure elements. Others, like water (H₂O), are compounds—made from two or more elements in fixed ratios, chemically bonded. Each compound has a unique formula, like CO₂ for carbon dioxide, representing its specific atomic arrangement. Compounds form molecules, tightly bonded units, creating an incredible diversity of substances in nature. https://cdn.kastatic.org/ka-youtube-converted/36nlbUdRvUM.mp4/36nlbUdRvUM.mp4 361 Formulae https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:stoichiometry-and-the-mole/x2613d8165d88df5e:mole-calculations/v/empirical-molecular-and-structural-formulas 2021-07-14T11:53:16Z Empirical, molecular, and structural formulas There are three main types of chemical formulas: empirical, molecular and structural. Empirical formulas show the simplest whole-number ratio of atoms in a compound, molecular formulas show the number of each type of atom in a molecule, and structural formulas show how the atoms in a molecule are bonded to each other. Sal Khan video https://cdn.kastatic.org/googleusercontent/3lBOW0TdgK9bg2nJfV9M2LPI0k4jQoqLRaSeQVWjhweBeFyR6BBl3ZE_WgpTxv2HJoc9VT_mTFPTyC2qBZai0Meu Empirical, molecular, and structural formulas There are three main types of chemical formulas: empirical, molecular and structural. Empirical formulas show the simplest whole-number ratio of atoms in a compound, molecular formulas show the number of each type of atom in a molecule, and structural formulas show how the atoms in a molecule are bonded to each other. https://cdn.kastatic.org/ka-youtube-converted/bmjg7lq4m4o.mp4/bmjg7lq4m4o.mp4 410 Formulae https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:atomic-structure-and-properties/x2eef969c74e0d802:valence-electrons-and-ionic-compounds/v/formula-for-ionic-compounds 2021-03-18T10:33:23Z Worked example: Finding the formula of an ionic compound To find the formula of an ionic compound, first identify the cation and write down its symbol and charge. Then, identify the anion and write down its symbol and charge. Finally, combine the two ions to form an electrically neutral compound. In this video, we'll walk through this process for the ionic compound calcium bromide. Sal Khan video https://cdn.kastatic.org/googleusercontent/uFzvQna9JIfbEJWn_g8kE_QLI6lwhccLp5EDsU3uvCI7eDoPW8Ot2aHw_IqS9s7G-M4WbFPK58RpSVckceItSlSJ Worked example: Finding the formula of an ionic compound To find the formula of an ionic compound, first identify the cation and write down its symbol and charge. Then, identify the anion and write down its symbol and charge. Finally, combine the two ions to form an electrically neutral compound. In this video, we'll walk through this process for the ionic compound calcium bromide. https://cdn.kastatic.org/ka-youtube-converted/8_fMpRUsnBk.mp4/8_fMpRUsnBk.mp4 179 Formulae https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-bonding/x2613d8165d88df5e:ionic-nomenclature/v/naming-ionic-compound-with-polyvalent-ion 2021-03-18T10:33:23Z Naming ionic compound with polyvalent ion Naming ionic compounds that contain polyvalent ions, using example of cobalt (III) sulfide. video https://cdn.kastatic.org/googleusercontent/sxisshpuJ9O_2ZZjQvIjFGtLso07gFMAoyk38AXaNrm0p6xisnDoq1wep1D35GeS_-3QwEcEQ-Q_Wx31ltj-MCoE Naming ionic compound with polyvalent ion Naming ionic compounds that contain polyvalent ions, using example of cobalt (III) sulfide. https://cdn.kastatic.org/ka-youtube-converted/vVTwzjvWySs.mp4/vVTwzjvWySs.mp4 242 Formulae https://www.khanacademy.org/science/chemistry/acids-and-bases-topic/copy-of-solubility-equilibria-mcat/v/common-polyatomic-ions 2021-02-15T02:44:57Z Common polyatomic ions Reviewing the common polyatomic ions, and explaining common suffixes and prefixes to help remember the formulas.  Jay video https://cdn.kastatic.org/googleusercontent/33vRsC7UGI-xHw8vLHVajCFPAUqsaY2J7OYNUUski1vkPTK2mXqNiHZQo8iri-3C2L9Azzs7jROQsC-5ZeCYR6I Common polyatomic ions Reviewing the common polyatomic ions, and explaining common suffixes and prefixes to help remember the formulas.  https://cdn.kastatic.org/ka-youtube-converted/DpnUrVXSLaQ.mp4/DpnUrVXSLaQ.mp4 348 Formulae https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:stoichiometry/x8bc8fb44369617ed:formulae/v/worked-example-formula-for-an-ionic-compound-ur 2025-08-08T00:24:37.843818748Z Worked example: Formula for an ionic compound Created by Khan Academy video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Worked example: Formula for an ionic compound Created by Khan Academy https://cdn.kastatic.org/ka-youtube-converted/NN83jv4mw8Q.mp4/NN83jv4mw8Q.mp4 211 Formulae https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:stoichiometry/x8bc8fb44369617ed:formulae/v/worked-example-writing-empirical-formulas-for-ionic-compounds 2022-10-31T23:33:27.733635026Z Worked example: writing empirical formulas for ionic compounds To write the empirical formula for an ionic compound, we use the periodic table to identify the metallic cation and the nonmetallic anion and write their symbols and charges. We then determine the ratio of each element to ensure a total charge of zero. Sal Khan video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Worked example: writing empirical formulas for ionic compounds To write the empirical formula for an ionic compound, we use the periodic table to identify the metallic cation and the nonmetallic anion and write their symbols and charges. We then determine the ratio of each element to ensure a total charge of zero. https://cdn.kastatic.org/ka-youtube-converted/ENJsWSCt_ac.mp4/ENJsWSCt_ac.mp4 354 Formulae https://www.khanacademy.org/science/bridge-course-class-11th-chemistry/x426c9d2c554669cb:basic-concepts-of-chemistry/x426c9d2c554669cb:ionic-compounds/e/find-the-formula-for-ionic-compounds 2025-02-06T18:17:42.147590351Z Find the formula for ionic compounds Practice finding the formula when given the name of an ionic compound. Yuki exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:stoichiometry/x8bc8fb44369617ed:formulae/e/formula-of-ionic-and-covalent-compounds 2026-04-29T07:20:45.495372596Z Formula of ionic and covalent compounds Check your understanding of identifying the formula of ionic and covalent compounds in this set of free practice questions. exercise https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-bonding/x2613d8165d88df5e:ionic-nomenclature/e/naming-main-group-ionic-compounds 2026-04-29T07:20:45.495372596Z Apply: Naming main group ionic compounds Apply your understanding of ionic nomenclature in this set of free, standards-aligned practice questions. donna fig exercise https://www.khanacademy.org/science/bridge-course-class-11th-chemistry/x426c9d2c554669cb:basic-concepts-of-chemistry/x426c9d2c554669cb:ionic-compounds/e/naming-ionic-compounds 2026-03-29T17:54:23.483136198Z Naming ionic compounds Practice naming ionic compounds when given the formula Yuki exercise https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:atoms-and-molecules/x46dd29ce84a663ea:writing-chemical-formulae/e/predicting-the-formula-of-the-given-ionic-compound 2026-03-06T09:40:40.837655949Z Predicting the formula of the given compound Let's solve a few problems to identify the correct formula of a given ionic compound. Aanchal Arora exercise https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-bonding/x2613d8165d88df5e:ionic-nomenclature/a/naming-ions-and-ionic-compounds 2026-04-26T16:30:39.382257956Z Learn and try: Naming ions and ionic compounds Learn how to name positive ions (cations), negative ions (anions), and ionic compounds involving main group elements. article https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-bonding/x2613d8165d88df5e:ionic-nomenclature/a/polyatomic-ions-article 2026-04-27T14:30:54.817409388Z Learn and try: Polyatomic ions Learn what polyatomic ions are and how to write them in chemical formulas. article https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:atoms-and-molecules/x46dd29ce84a663ea:molecules-and-ions/a/naming-monatomic-ions-and-ionic-compounds 2021-04-29T07:59:16Z Naming monatomic ions and ionic compounds Learn how to name monatomic ions and ionic compounds containing monatomic ions, predict charges for monatomic ions, and understand formulas.  article https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:stoichiometry/x8bc8fb44369617ed:formulae/v/chemical-equations 2025-03-21T20:29:57.678923887Z Chemical equations Chemical equations use symbols and formulas to represent chemical reactions. Reactants, on the left, rearrange to form products, on the right. The law of conservation of matter states that atoms cannot be created or destroyed, so equations must be balanced using coefficients to ensure the same number of each atom appears on both sides. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/d3564b9f-eec6-4925-a114-6533dffea9c2_1280_720_base.png Chemical equations Chemical equations use symbols and formulas to represent chemical reactions. Reactants, on the left, rearrange to form products, on the right. The law of conservation of matter states that atoms cannot be created or destroyed, so equations must be balanced using coefficients to ensure the same number of each atom appears on both sides. https://cdn.kastatic.org/ka-youtube-converted/_c6wm4jl8BU.mp4/_c6wm4jl8BU.mp4 485 Formulae https://www.khanacademy.org/science/chemistry/chemical-reactions-stoichiome/balancing-chemical-equations/v/chemical-reactions-introduction 2021-04-11T17:58:19Z Chemical reactions introduction Reactants and products in reversible and irreversible chemical reactions. video https://cdn.kastatic.org/googleusercontent/sOAB7bEWaCpnU94w4SBtJMJRngkzJJM19enomEj_DjdKizQ4PcjKW8uzQ5GItii7yeMnOf8Gxaa_ZLbYDhDrtKM Chemical reactions introduction Reactants and products in reversible and irreversible chemical reactions. https://cdn.kastatic.org/ka-youtube-converted/TStjgUmL1RQ.mp4/TStjgUmL1RQ.mp4 553 Formulae https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:stoichiometry/x8bc8fb44369617ed:formulae/v/worked-examples-balancing-chemical-equations 2025-03-21T20:29:57.678923887Z Worked examples: Balancing chemical equations Balancing chemical equations ensures they follow the law of conservation of matter—atoms are neither created nor destroyed, only rearranged. We adjust coefficients, not subscripts, to equalize atom counts on both sides of the equation. Coefficients must be in their simplest whole-number ratio to accurately represent the reaction. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/39c711a7-6e08-4746-a59e-b633f650a089_1280_720_base.png Worked examples: Balancing chemical equations Balancing chemical equations ensures they follow the law of conservation of matter—atoms are neither created nor destroyed, only rearranged. We adjust coefficients, not subscripts, to equalize atom counts on both sides of the equation. Coefficients must be in their simplest whole-number ratio to accurately represent the reaction. https://cdn.kastatic.org/ka-youtube-converted/Z2IOoAhQbX4.mp4/Z2IOoAhQbX4.mp4 464 Formulae https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:chemical-reactions/x2eef969c74e0d802:net-ionic-equations/v/complete-ionic-and-net-ionic-equations 2021-07-14T12:25:41Z Molecular, complete ionic, and net ionic equations In the molecular equation for a reaction, all of the reactants and products are represented as neutral molecules (even soluble ionic compounds and strong acids). In the complete ionic equation, soluble ionic compounds and strong acids are rewritten as dissociated ions. In the net ionic equation, any ions that do not participate in the reaction (called spectator ions) are excluded. As a result, the net ionic equation shows only the species that are actually involved in the chemical reaction. Sal Khan video https://cdn.kastatic.org/googleusercontent/rTNFxxqtzcIBxqpDfK0pY1E1_sdjuZkWqXvuRIv7SqXpaSQj6N_33EIq45q2z6bThYwzAibEa9UneSbpBrsBrhsu9A Molecular, complete ionic, and net ionic equations In the molecular equation for a reaction, all of the reactants and products are represented as neutral molecules (even soluble ionic compounds and strong acids). In the complete ionic equation, soluble ionic compounds and strong acids are rewritten as dissociated ions. In the net ionic equation, any ions that do not participate in the reaction (called spectator ions) are excluded. As a result, the net ionic equation shows only the species that are actually involved in the chemical reaction. https://cdn.kastatic.org/ka-youtube-converted/BgTpPM9BMuU.mp4/BgTpPM9BMuU.mp4 355 Formulae https://www.khanacademy.org/science/chemistry/acids-and-bases-topic/copy-of-solubility-equilibria-mcat/v/dissolution-and-precipitation 2021-01-04T18:35:18Z Dissolution and precipitation Defining solute, solvent, hydration, dissolution, precipitation, net ionic equation, and spectator ions. Looking at the molecular level interactions between water and ions in NaCl.  Jay video https://cdn.kastatic.org/googleusercontent/kDMmlsQun-CdEXllAr95001kgttnuJ3S9I_RbJ2JZhMp3zCp7PAG0BewlmJXzHmkE2E_mSoJhpNMvJ85XHBCd85Tbg Dissolution and precipitation Defining solute, solvent, hydration, dissolution, precipitation, net ionic equation, and spectator ions. Looking at the molecular level interactions between water and ions in NaCl.  https://cdn.kastatic.org/ka-youtube-converted/g_snytB7iQ0.mp4/g_snytB7iQ0.mp4 600 Formulae https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-reactions/x2613d8165d88df5e:representing-chemical-reactions/e/apply-representing-chemical-reactions 2026-04-28T11:00:37.315336883Z Apply: Representing chemical reactions Apply your understanding of using chemical equations to represent chemical reactions in this set of free practice questions. Fig exercise https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-reactions/x2613d8165d88df5e:balancing-chemical-equations/e/apply-balancing-equations 2026-04-29T07:20:45.495372596Z Apply: Balancing equations Apply your understanding of the conservation of matter in chemical equations in this set of free practice questions. Fig exercise https://www.khanacademy.org/science/bridge-course-class-11th-chemistry/x426c9d2c554669cb:types-of-chemical-reactions/x426c9d2c554669cb:different-types-of-chemical-reactions/e/balancing-simple-chemical-equations 2025-03-07T16:50:49.734868403Z Balancing simple chemical equations Let's solve some questions! vibhor exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:stoichiometry/x8bc8fb44369617ed:formulae/e/balancing-chemical-equations-new 2026-03-27T14:53:23.229071668Z Balancing chemical equations Let's practice balancing chemical equations. exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:stoichiometry/x8bc8fb44369617ed:formulae/e/balancing_chemical_equations 2026-03-24T23:41:07.080866137Z Balancing chemical equations 1 Practice balancing chemical equations Ben Eater exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:stoichiometry/x8bc8fb44369617ed:formulae/a/balancing-chemical-equations 2026-04-29T07:20:45.495372596Z Learn and try: Balancing chemical equations Learn how to balance chemical equations by ensuring the same number of each type of atom appears on both sides of the equation. Explore why chemical equations must be balanced and the step-by-step process for achieving balance. article https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:stoichiometry/x8bc8fb44369617ed:formulae/a/chemical-equations 2026-04-29T07:20:45.495372596Z Learn and try: Chemical equations Learn how to read and interpret chemical equations that represent what happens during chemical reactions. Discover how chemical equations show the reactants that combine and the products that form, along with the story they tell about the reaction. article https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-reactions/x2613d8165d88df5e:representing-chemical-reactions/a/symbols-in-chemical-equations 2026-04-28T11:00:37.315336883Z Learn and try: Symbols in chemical equations Learn the meaning behind the symbols we use to represent chemical reactions. article https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:chemical-reactions/x2eef969c74e0d802:net-ionic-equations/e/net-ionic-equations 2021-04-29T08:01:32Z Net ionic equations Check your understanding of net ionic equations in this set of free practice questions designed for AP Chemistry students. exercise https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:chemical-reactions/x2eef969c74e0d802:net-ionic-equations/a/complete-ionic-and-net-ionic-equations 2022-01-11T22:17:00.362877679Z Molecular, complete ionic, and net ionic equations article