valence

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valence (valency) Measure of the ‘combining power’ of a particular element, equal to the number of single chemical bonds one atom can form, or the number of electrons it gives up or accepts when forming a compound. Hydrogen has a valency of 1, carbon 4, and sulphur 2, as seen in compounds such as methane (CH4), carbon disulphide (CS2), and hydrogen sulphide (H2S). See also atomic number; covalent bond; ionic bond

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