https://www.khanacademy.org/science/ap-biology/chemistry-of-life/elements-of-life/v/elements-and-atoms 2023-03-31T23:16:47.953017837Z Elements and atoms Elements are pure substances with specific properties. Atoms are the smallest units of elements that still retain the element's properties. Atoms contain electrons, neutrons, and protons. Each element is defined by the number of protons in its nucleus. Sal Khan video https://cdn.kastatic.org/googleusercontent/zfLHeNHjPfEhSYfKtZLu6Ft_uFg2p_L9gALjUyfahbjdBzZbrDLxrg-rk_mrsUBBVIKs44ALBBI1Gv8cm2O_Ppa05g Elements and atoms Elements are pure substances with specific properties. Atoms are the smallest units of elements that still retain the element's properties. Atoms contain electrons, neutrons, and protons. Each element is defined by the number of protons in its nucleus. https://cdn.kastatic.org/ka-youtube-converted/IFKnq9QM6_A.mp4/IFKnq9QM6_A.mp4 789 Periodic table 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 Periodic table 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 Periodic table https://www.khanacademy.org/science/ap-biology/chemistry-of-life/elements-of-life/a/matter-elements-atoms-article 2021-04-29T08:02:50Z Matter, elements, and atoms Learn about the structure of the atom, and how atoms make up matter. An atom is the smallest unit of matter that retains all of the chemical properties of an element.  article https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atomic-models-and-periodicity/x2613d8165d88df5e:the-periodic-table/a/determine-valence-electrons-using-the-periodic-table 2026-04-26T16:30:39.382257956Z Learn: Determine valence electrons using the periodic table Learn how to determine the number of valence electrons for an element using the periodic table. article https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:atomic-structure-and-the-periodic-table/v/given-atomic-number-find-position-and-vice-versa-solved-example-ur 2025-08-08T00:24:37.843818748Z Given atomic number find position and vice-versa (Solved example) Created by Khan Academy video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Given atomic number find position and vice-versa (Solved example) Created by Khan Academy https://cdn.kastatic.org/ka-youtube-converted/DzLEbHyZC9I.mp4/DzLEbHyZC9I.mp4 668 Periodic table https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:atomic-structure-and-the-periodic-table/e/find-the-group-and-period-number-of-an-element 2021-04-29T07:51:19Z Find the group and period of an element Let's practice to find position of an element in the periodic table by finding out the 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--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