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 Patterns in the periodic table https://www.khanacademy.org/science/chemistry/atomic-structure-and-properties/copy-of-periodic-table-of-elements/v/periodic-table-groups 2022-09-07T08:21:01.673602243Z Groups of the periodic table The s-, p-, and d-block elements of the periodic table are arranged into 18 numbered columns, or groups. The elements in each group have the same number of valence electrons. As a result, elements in the same group often display similar properties and reactivity. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/bf6fd19a-167e-41d3-a67f-7032ecf1249b_1280_720_base.png Groups of the periodic table The s-, p-, and d-block elements of the periodic table are arranged into 18 numbered columns, or groups. The elements in each group have the same number of valence electrons. As a result, elements in the same group often display similar properties and reactivity. https://cdn.kastatic.org/ka-youtube-converted/jQGUkJc7_04.mp4/jQGUkJc7_04.mp4 461 Patterns in the periodic table https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atomic-models-and-periodicity/x2613d8165d88df5e:periodic-trends/v/atomic-radii-trends 2023-12-15T18:39:28.793791463Z Atomic radii trends Atoms are not all the same size. The relative size of the atoms follows a set of trends on the periodic table. Going across a period, the main group elements tend to decrease in atomic radius due to the increased nuclear charge. Going down a group, the main group elements tend to increase in atomic radius due to increased shielding and the addition of new shells to the structure of the atom. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/b20fde22-88b0-4dfa-8d69-9a73f51373fa_1280_720_base.png Atomic radii trends Atoms are not all the same size. The relative size of the atoms follows a set of trends on the periodic table. Going across a period, the main group elements tend to decrease in atomic radius due to the increased nuclear charge. Going down a group, the main group elements tend to increase in atomic radius due to increased shielding and the addition of new shells to the structure of the atom. https://cdn.kastatic.org/ka-youtube-converted/RrwL99bEotk.mp4/RrwL99bEotk.mp4 288 Patterns in the periodic table https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atomic-models-and-periodicity/x2613d8165d88df5e:periodic-trends/e/apply-atomic-radii-trends 2026-04-27T10:10:46.754795089Z Apply: Atomic radii trends Apply your understanding of atomic radii trends in this set of free practice questions. Eric exercise https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atomic-models-and-periodicity/x2613d8165d88df5e:periodic-trends/v/ionization-energy-trends-hs 2023-12-15T18:39:28.793791463Z Ionization energy trends Ionization is the process of removing an electron from a neutral atom (or compound). The energy required to remove an electron is the ionization energy. The ionization energy differs for each atom. There are trends that match the structure of the periodic table. Across a period, ionization energy tends to increase. Down a group, the ionization energy tends to decrease. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/44ba4dcb-7ee8-4816-ae19-d37081115519_1280_720_base.png Ionization energy trends Ionization is the process of removing an electron from a neutral atom (or compound). The energy required to remove an electron is the ionization energy. The ionization energy differs for each atom. There are trends that match the structure of the periodic table. Across a period, ionization energy tends to increase. Down a group, the ionization energy tends to decrease. https://cdn.kastatic.org/ka-youtube-converted/MyBYZJ3Wo_0.mp4/MyBYZJ3Wo_0.mp4 272 Patterns in the periodic table https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atomic-models-and-periodicity/x2613d8165d88df5e:periodic-trends/e/apply-ionization-energy-trends 2026-04-27T10:10:46.754795089Z Apply: Ionization energy trends Apply your understanding of ionization energy trends in this set of free practice questions. Eric exercise https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:states-of-matter/x2613d8165d88df5e:electronegativity-and-bond-polarity/v/electronegativity-trends 2023-12-18T19:15:22.874322042Z Electronegativity Electronegativity is a measure of an atom's ability to attract shared electrons to itself. On the periodic table, electronegativity generally increases as you move from left to right across a period and decreases as you move down a group. As a result, the most electronegative elements are found on the top right of the periodic table, while the least electronegative elements are found on the bottom left. Sal Khan video https://cdn.kastatic.org/googleusercontent/XVZZWl3QefXzCno4AIeKJyHHEUJsTuK3Q5rTYoUKrtH2rV2sjLh7quXzB1WfmnVK8uSbDuqLaXPvjDmv6vfo-MAu Electronegativity Electronegativity is a measure of an atom's ability to attract shared electrons to itself. On the periodic table, electronegativity generally increases as you move from left to right across a period and decreases as you move down a group. As a result, the most electronegative elements are found on the top right of the periodic table, while the least electronegative elements are found on the bottom left. https://cdn.kastatic.org/ka-youtube-converted/Rr7LhdSKMxY.mp4/Rr7LhdSKMxY.mp4 594 Patterns in the periodic table