https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:the-periodic-table/x8bc8fb44369617ed:arrangement-of-elements/v/the-periodic-table 2025-01-16T17:32:17.772857468Z The periodic table The periodic table organizes all known elements by atomic number, displaying them in rows and columns called periods and groups. Each element’s square includes its symbol, atomic number, and atomic mass. Groups of elements often share similar properties, like the reactive metals in Group 1, and the inert noble gases in Group 18. The table also separates metals, nonmetals, and metalloids, helping us see patterns in elemental behavior and relationships. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/b9616325-fb03-4e51-a4a5-b2c376f599e8_1280_720_base.png The periodic table The periodic table organizes all known elements by atomic number, displaying them in rows and columns called periods and groups. Each element’s square includes its symbol, atomic number, and atomic mass. Groups of elements often share similar properties, like the reactive metals in Group 1, and the inert noble gases in Group 18. The table also separates metals, nonmetals, and metalloids, helping us see patterns in elemental behavior and relationships. https://cdn.kastatic.org/ka-youtube-converted/Jg3Fo4WD8XE.mp4/Jg3Fo4WD8XE.mp4 417 Arrangement of elements https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atomic-models-and-periodicity/x2613d8165d88df5e:the-periodic-table/v/periodic-table-introduction 2024-01-03T14:14:18.294406117Z The periodic table The periodic table organizes elements into groups and periods based on their chemical and physical properties. Elements in the same group share similar characteristics, like reactivity. The table is divided into metals, nonmetals, and metalloids, each with distinct properties. Key groups include alkali metals, alkaline earth metals, halogens, and noble gases. Jay video https://cdn.kastatic.org/googleusercontent/93FeEfrl_y0KtM_WRXilR41NTHLkCZ-Nkru8Ur4Uil0CjC7YODnZxTQs3PHhbj3zTCj1qgPwosPW2wBJP-nUnaRw The periodic table The periodic table organizes elements into groups and periods based on their chemical and physical properties. Elements in the same group share similar characteristics, like reactivity. The table is divided into metals, nonmetals, and metalloids, each with distinct properties. Key groups include alkali metals, alkaline earth metals, halogens, and noble gases. https://cdn.kastatic.org/ka-youtube-converted/t_f8bB1kf6M.mp4/t_f8bB1kf6M.mp4 536 Arrangement of elements https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-bonding/x2613d8165d88df5e:ionic-bonds/v/valence-electrons-and-ionic-compounds 2022-09-07T08:21:01.673602243Z Valence electrons and ionic compounds When forming ions, elements typically gain or lose the minimum number of electrons necessary to achieve a full octet. For example, fluorine has seven valence electrons, so it is most likely to gain one electron to form an ion with a 1- charge. We can use this method to predict the charges of ions in ionic compounds. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/0fa65651-5c25-4356-ab62-0ddbdaf7cdb5_1280_720_base.png Valence electrons and ionic compounds When forming ions, elements typically gain or lose the minimum number of electrons necessary to achieve a full octet. For example, fluorine has seven valence electrons, so it is most likely to gain one electron to form an ion with a 1- charge. We can use this method to predict the charges of ions in ionic compounds. https://cdn.kastatic.org/ka-youtube-converted/XPnlIEk7XrU.mp4/XPnlIEk7XrU.mp4 475 Arrangement of elements https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-bonding/x2613d8165d88df5e:ionic-bonds/e/apply-predicting-ion-formation 2026-04-29T07:20:45.495372596Z Apply: Predicting ion formation Apply your knowledge of trends in ion formation in this set of free practice questions. Emily Cizmas exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:the-periodic-table/x8bc8fb44369617ed:arrangement-of-elements/e/apply-periodic-table 2026-04-29T07:20:45.495372596Z Apply: The periodic table Apply your understanding of the periodic table in this set of free, standards-aligned practice questions. Allen Ruch exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:the-periodic-table/x8bc8fb44369617ed:arrangement-of-elements/e/groups-and-periods--find-the-atomic-number 2021-04-29T07:53:56Z Groups and periods: find the atomic number Let's practice on finding the atomic number of an element by knowing its group and period number. Chaitra exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:the-periodic-table/x8bc8fb44369617ed:arrangement-of-elements/e/groups-and-periods--position-of-elements 2026-02-27T12:30:36.531197313Z Identify the elements belonging to the same group or period Let's practice identifying elements belonging to the same period or the group by writing their electronic configuration. Also, knowing the reasons for belonging to the same period or the group. Chaitra exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:the-periodic-table/x8bc8fb44369617ed:arrangement-of-elements/e/periodic-trend--metallic---nonmetallic-characters--electropositivity---electronegativity 2026-02-27T12:30:36.531197313Z Periodic trends: metallic, nonmetallic, electropositive, & electronegative characters Let's practice to identify the periodic trends of losing and gaining and electrons when we go from left to right and top to bottom of the periodic table. Chaitra exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:the-periodic-table/x8bc8fb44369617ed:arrangement-of-elements/e/identify-metals-and-nonmetals-in-the-periodic-table 2026-02-27T12:30:36.531197313Z Identify metals and nonmetals in the periodic table Let's test our understanding of metals and nonmetals by identifying them from the given atomic numbers and position of the elements in the periodic table. exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:the-periodic-table/x8bc8fb44369617ed:arrangement-of-elements/v/periodic-trend-of-metallic-character-pk 2025-12-31T05:23:06.848711158Z Periodic trend of Metallic character Metallic character can be measured by the ease of an element to give away its valence electrons. It depends on the valence electron’s i) effective nuclear charge (ENC) and ii) distance from the nucleus. Let's see what's the periodic trend of Metallic character. Created by Ram Prakash. Khan Academy video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Periodic trend of Metallic character Metallic character can be measured by the ease of an element to give away its valence electrons. It depends on the valence electron’s i) effective nuclear charge (ENC) and ii) distance from the nucleus. Let's see what's the periodic trend of Metallic character. Created by Ram Prakash. https://cdn.kastatic.org/ka-youtube-converted/vllob73uwR4.mp4/vllob73uwR4.mp4 882 Arrangement of elements https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:atomic-structure-and-properties/x2eef969c74e0d802:periodic-trends/v/atomic-and-ionic-radii 2021-01-04T18:35:18Z Atomic and ionic radii Atomic and ionic radii are found by measuring the distances between atoms and ions in chemical compounds. On the periodic table, atomic radius generally decreases as you move from left to right across a period (due to increasing nuclear charge) and increases as you move down a group (due to the increasing number of electron shells). Similar trends are observed for ionic radius, although cations and anions need to be considered separately. Jay video https://cdn.kastatic.org/googleusercontent/OtLCosmSgkrprxD8aa4wAgHHnV9yR8ALfEAbwQdK7VHWSabodfCPHuwxsP86c4KCwvHfMzvUnzjEIaidEYOz31xo7Q Atomic and ionic radii Atomic and ionic radii are found by measuring the distances between atoms and ions in chemical compounds. On the periodic table, atomic radius generally decreases as you move from left to right across a period (due to increasing nuclear charge) and increases as you move down a group (due to the increasing number of electron shells). Similar trends are observed for ionic radius, although cations and anions need to be considered separately. https://cdn.kastatic.org/ka-youtube-converted/rKoIcgBM4Vg.mp4/rKoIcgBM4Vg.mp4 686 Arrangement of elements https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:the-periodic-table/x8bc8fb44369617ed:arrangement-of-elements/e/valence-electrons-and-chemical-similarities 2021-04-29T07:49:56Z Identify elements with similar chemical properties Let's practice identifying the elements with similar chemical properties by finding the valence electrons of the given elements. exercise