Charge Number

Charge number or just valance of an ion is the coefficient that, when multiplied by the elementary charge, gives the ion's charge.

For example, the charge on a chloride ion, is, where e is the elementary charge. This means the charge number for the ion is .

is sometimes used as the symbol for the charge number. In that case, the charge of an ion could be written as .

For an atomic nucleus, which can be regarded as an ion having stripped off all electrons, the charge number is identical with the atomic number Z (number of protons).

In particle physics the charge number is a (derived) flavour quantum number, mostly denoted by Q (regarded as 'electric charge in units of e') rather than z. For color charged particles with like quarks and hypothetical leptoquarks the charge number is a broken multiple of 1/3.