https://www.khanacademy.org/science/ms-chemistry/xc370bc422b7f75fc:classifying-matter/xc370bc422b7f75fc:elements-and-atoms/v/elements 2025-01-16T17:32:17.772857468Z Elements Elements are the fundamental building blocks of all matter, just as letters form the basis of all writing. With only about 100 natural elements, nature constructs everything around us—from tiny microbes to vast oceans and stars. These elements, represented by symbols on the periodic table, combine in countless ways to create the diverse materials that make up the universe. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/7bad28ff-1c16-4904-860d-48ebd21ceb41_1280_720_base.png Elements Elements are the fundamental building blocks of all matter, just as letters form the basis of all writing. With only about 100 natural elements, nature constructs everything around us—from tiny microbes to vast oceans and stars. These elements, represented by symbols on the periodic table, combine in countless ways to create the diverse materials that make up the universe. https://cdn.kastatic.org/ka-youtube-converted/PeNjuIQFd9U.mp4/PeNjuIQFd9U.mp4 313 Periodic table https://www.khanacademy.org/science/ms-chemistry/xc370bc422b7f75fc:classifying-matter/xc370bc422b7f75fc:elements-and-atoms/v/atoms 2025-01-16T17:32:17.772857468Z Atoms An atom is the smallest particle of an element that still retains all the properties of that element. Early philosophers imagined atoms as indivisible units that make up all matter, an idea revived and developed by scientists like John Dalton. Atoms are incredibly small and numerous—a single gold ring contains more atoms than stars in the universe, highlighting their fundamental role in forming the matter we see. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/6f8dc03b-b8ae-49fe-b3c7-28487059ceae_1280_720_base.png Atoms An atom is the smallest particle of an element that still retains all the properties of that element. Early philosophers imagined atoms as indivisible units that make up all matter, an idea revived and developed by scientists like John Dalton. Atoms are incredibly small and numerous—a single gold ring contains more atoms than stars in the universe, highlighting their fundamental role in forming the matter we see. https://cdn.kastatic.org/ka-youtube-converted/KyBgxe-rU48.mp4/KyBgxe-rU48.mp4 248 Periodic table https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:atoms-and-molecules/x46dd29ce84a663ea:what-is-an-atom/e/understand-elements-and-atoms 2026-04-20T04:40:44.098027975Z Understand: elements and atoms Check your understanding of elements and atoms in this set of free, standards-aligned practice questions. Allen Ruch exercise https://www.khanacademy.org/science/ms-chemistry/xc370bc422b7f75fc:classifying-matter/xc370bc422b7f75fc:elements-and-atoms/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/ms-chemistry/xc370bc422b7f75fc:classifying-matter/xc370bc422b7f75fc:elements-and-atoms/a/elements-atoms-and-the-periodic-table 2026-04-17T11:10:45.679633951Z Learn and try: Elements, atoms, and the periodic table Learn about the basic building blocks of all matter and how atoms of different elements have unique properties. Discover how elements are organized on the periodic table and what makes each element distinct. article https://www.khanacademy.org/science/ms-chemistry/xc370bc422b7f75fc:classifying-matter/xc370bc422b7f75fc:elements-and-atoms/e/understand-the-periodic-table 2026-03-11T01:40:33.014543209Z Understand: the periodic table Check your understanding of the periodic table in this set of free, standards-aligned practice questions. Allen Ruch exercise https://www.khanacademy.org/science/ms-chemistry/xc370bc422b7f75fc:classifying-matter/xc370bc422b7f75fc:elements-and-atoms/e/apply-periodic-table 2025-08-07T15:47:52.529438553Z 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/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/hs-chemistry/x2613d8165d88df5e:atomic-models-and-periodicity/x2613d8165d88df5e:the-periodic-table/e/understand-structure-of-the-periodic-table 2026-03-09T16:00:33.246773958Z Understand: structure of the periodic table Check your understanding of the structure of the periodic table in this set of free, standards-aligned practice questions. Donna fig exercise https://www.khanacademy.org/science/grade-9-chemistry-snc-aligned/x22d5b83c2ea2dc38:periodic-table-and-periodicity/x22d5b83c2ea2dc38:features-of-modern-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/grade-9-chemistry-snc-aligned/x22d5b83c2ea2dc38:periodic-table-and-periodicity/x22d5b83c2ea2dc38:features-of-modern-periodic-table/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/grade-9-chemistry-snc-aligned/x22d5b83c2ea2dc38:periodic-table-and-periodicity/x22d5b83c2ea2dc38:features-of-modern-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/strengthened-shs-chemistry-1/x174677b2bfa4bea2:1st-quarter/x174677b2bfa4bea2:periodic-table-and-electron-configurations/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/hs-chemistry/x2613d8165d88df5e:atomic-models-and-periodicity/x2613d8165d88df5e:the-quantum-model/v/electron-configurations-with-the-periodic-table 2024-08-16T15:18:47.217883837Z Electron configurations with the periodic table The periodic table is organized by grouping elements with similar chemical properties and electron structures. An element's location on the table can be used to determine its electron configuration. By following the order of periods (rows) and blocks (s, p, d, f), you can trace how electrons fill the atom's orbitals and efficiently determine the distribution of electrons in an atom. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/97662d3a-39a7-4057-b45f-756dcd05369c_1280_720_base.png Electron configurations with the periodic table The periodic table is organized by grouping elements with similar chemical properties and electron structures. An element's location on the table can be used to determine its electron configuration. By following the order of periods (rows) and blocks (s, p, d, f), you can trace how electrons fill the atom's orbitals and efficiently determine the distribution of electrons in an atom. https://cdn.kastatic.org/ka-youtube-converted/hwqLCwgo6SU.mp4/hwqLCwgo6SU.mp4 879 Periodic table https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atomic-models-and-periodicity/x2613d8165d88df5e:the-periodic-table/a/determine-valence-electrons-using-the-periodic-table 2025-03-12T16:31:14.708488543Z 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/hs-chemistry/x2613d8165d88df5e:atomic-models-and-periodicity/x2613d8165d88df5e:the-quantum-model/a/the-periodic-table-electron-shells-and-orbitals-article 2024-02-03T14:54:13.458936091Z The periodic table, electron shells, and orbitals article https://www.khanacademy.org/science/grade-9-chemistry-snc-aligned/x22d5b83c2ea2dc38:chemical-bonding/x22d5b83c2ea2dc38:chemical-properties-of-main-group-elements/e/find-the-valence-electrons 2021-04-29T07:57:02Z Find the valence electrons Let's practice on finding the valence electrons of an element by counting the number of electrons present in the outermost shell. Chaitra exercise https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atomic-models-and-periodicity/x2613d8165d88df5e:the-quantum-model/e/apply-electron-configurations 2026-03-11T21:50:47.587134886Z Apply: electron configurations Apply your understanding of electron configurations in this set of free practice questions. Allen Ruch exercise