Since metal ions bear a charge equal to their spectroscopic oxidation state only in the gas phase, it is necessary to consider how the positive charge is reduced for the chemically combined ion and also to devise criteria for assigning this charge. Here it is shown how interelectronic repulsion energies, obtained from optical spectroscopy, can be exploited, and the method is exemplified for the Tl+ ion to show how its effective charge decreases with increasing basicity of the glass. Trends are reported for the alkali metal ions, especially in berate glasses where two types of site have been shown to exist. Consideration is also given to the degree of negative charge, provided by the oxygen atoms of the glass, at sites for the metal ions.