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  2. Periodic trends - Wikipedia

    en.wikipedia.org/wiki/Periodic_trends

    The periodic trends in properties of elements. In chemistry, periodic trends are specific patterns present in the periodic table that illustrate different aspects of certain elements when grouped by period and/or group. They were discovered by the Russian chemist Dmitri Mendeleev in 1863.

  3. History of the periodic table - Wikipedia

    en.wikipedia.org/wiki/History_of_the_periodic_table

    This is an accepted version of this page This is the latest accepted revision, reviewed on 28 January 2025. Development of the table of chemical elements The American chemist Glenn T. Seaborg —after whom the element seaborgium is named—standing in front of a periodic table, May 19, 1950 Part of a series on the Periodic table Periodic table forms 18-column 32-column Alternative and extended ...

  4. Ionization energy - Wikipedia

    en.wikipedia.org/wiki/Ionization_energy

    The two electrons in the same orbital are closer together on average than two electrons in different orbitals, so that they shield each other from the nucleus more effectively and it is easier to remove one electron, resulting in a lower ionization energy. [2] [13] Furthermore, after every noble gas element, the ionization energy drastically drops.

  5. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    Periodic table of the chemical elements showing the most or more commonly named sets of elements (in periodic tables), and a traditional dividing line between metals and nonmetals. The f-block actually fits between groups 2 and 3 ; it is usually shown at the foot of the table to save horizontal space.

  6. History of atomic theory - Wikipedia

    en.wikipedia.org/wiki/History_of_atomic_theory

    [35]: 118 Moreover, the periodic table could predict how many atoms of other elements that an atom could bond with — e.g., germanium and carbon are in the same group on the table and their atoms both combine with two oxygen atoms each (GeO 2 and CO 2). Mendeleev found these patterns validated atomic theory because it showed that the elements ...

  7. Electron configuration - Wikipedia

    en.wikipedia.org/wiki/Electron_configuration

    The periodicity of the periodic table in terms of periodic table blocks is due to the number of electrons (2, 6, 10, and 14) needed to fill s, p, d, and f subshells. These blocks appear as the rectangular sections of the periodic table.

  8. Alkaline earth metal - Wikipedia

    en.wikipedia.org/wiki/Alkaline_earth_metal

    The alkaline earth metals have the second-lowest first ionization energies in their respective periods of the periodic table [4] because of their somewhat low effective nuclear charges and the ability to attain a full outer shell configuration by losing just two electrons. The second ionization energy of all of the alkaline metals is also ...

  9. Types of periodic tables - Wikipedia

    en.wikipedia.org/wiki/Types_of_periodic_tables

    1992 — Magarshak & Malinsky's three-dimensional periodic table: Quantum mechanics-based table with group 3 as Sc-Y-La-Ac [104] 2003 — Graphic representations of the periodic system: As a building [105] 2003 — Two-amphitheatre pyramid periodic table [106] 2011 — Aldersley 3D periodic table: As four apartments [107]