charge number

in inorganic nomenclature
The magnitude of the charge on an ion, given in arabic numerals followed by the sign of the charge, in parentheses without a space, immediately after the name of an ion, e.g. iron(2+), hexacyanoferrate(4−).
The term @E02231@ is no longer recommended.
Red Book, 3rd ed., p. 66 [Terms] [Book]