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  2. Selenium - Wikipedia

    en.wikipedia.org/wiki/Selenium

    Electron configuration 3d 10 4s 2 4p 4: Electrons per shell: 2, 8, 18, 6: Physical properties; ... Selenium is a chemical element; it has the symbol Se and atomic ...

  3. Electron configurations of the elements (data page) - Wikipedia

    en.wikipedia.org/wiki/Electron_configurations_of...

    This page shows the electron configurations of the neutral gaseous atoms in their ground states. For each atom the subshells are given first in concise form, then with all subshells written out, followed by the number of electrons per shell. For phosphorus (element 15) as an example, the concise form is [Ne] 3s 2 3p 3.

  4. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows (" periods ") and columns (" groups "). It is an icon of chemistry and is widely used in physics and other sciences. It is a depiction of the periodic law, which states that when the elements are arranged in order ...

  5. Period 4 element - Wikipedia

    en.wikipedia.org/wiki/Period_4_element

    A period 4 element is one of the chemical elements in the fourth row (or period) of the periodic table of the chemical elements.The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall ...

  6. Electron configuration - Wikipedia

    en.wikipedia.org/wiki/Electron_configuration

    Contents. Electron configuration. In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. [ 1 ] For example, the electron configuration of the neon atom is 1s2 2s2 2p6, meaning that the 1s, 2s, and 2p subshells are ...

  7. d-block contraction - Wikipedia

    en.wikipedia.org/wiki/D-block_contraction

    The d-block contraction (sometimes called scandide contraction[1]) is a term used in chemistry to describe the effect of having full d orbitals on the period 4 elements. The elements in question are gallium, germanium, arsenic, selenium, bromine, and krypton [citation needed]. Their electronic configurations include completely filled d orbitals ...

  8. Aufbau principle - Wikipedia

    en.wikipedia.org/wiki/Aufbau_principle

    For example, in copper 29 Cu, according to the Madelung rule, the 4s subshell (n + l = 4 + 0 = 4) is occupied before the 3d subshell (n + l = 3 + 2 = 5). The rule then predicts the electron configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 9 4s 2, abbreviated [Ar] 3d 9 4s 2 where [Ar] denotes the configuration of argon, the preceding noble gas.

  9. Chalcogen - Wikipedia

    en.wikipedia.org/wiki/Chalcogen

    The chalcogens (ore forming) (/ ˈkælkədʒənz / KAL-kə-jənz) are the chemical elements in group 16 of the periodic table. [1] This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive elements polonium (Po) and livermorium (Lv). [2]