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Core electrons are the electrons in an atom that are not valence electrons and do not participate in chemical bonding.[1] The nucleus and the core electrons of an atom form the atomic core. Core electrons are tightly bound to the nucleus. Therefore, unlike valence electrons, core electrons play a secondary role in chemical bonding and reactions by screening the positive charge of the atomic nucleus from the valence electrons.[2]
The number of valence electrons of an element can be determined by the periodic table group of the element (see valence electron):
- For main-group elements, the number of valence electrons ranges from 1 to 8 (ns and np orbitals).
- For transition metals, the number of valence electrons ranges from 3 to 12 (ns and (n−1)d orbitals).
- For lanthanides and actinides, the number of valence electrons ranges from 3 to 16 (ns, (n−2)f and (n−1)d orbitals).
All other non-valence electrons for an atom of that element are considered core electrons.
- ^ Rassolov, Vitaly A.; Pople, John A.; Redfern, Paul C.; Curtiss, Larry A. (2001-12-28). "The definition of core electrons". Chemical Physics Letters. 350 (5–6): 573–576. Bibcode:2001CPL...350..573R. doi:10.1016/S0009-2614(01)01345-8.
- ^ Miessler, G. L. (1999). Inorganic Chemistry. Prentice Hall.