How is the charge of an atom of a transition metal determined?
I’m not sure whether you mean experimentally or in terms of nomenclature. If you are presented with a transition metal compound of unknown composition there are many ways to deduce the charge of the metal ion. If the anion is known then titration could be used to determine concentrations, eg if you have a charge neutral species and twice the concentration of the anion than cation, then the cation charge is twice the charge on the anion. Typical reactive patterns can also be used, Cu2+ has a low tendency to form [Cu(NH3)6]2+ preferring four ammonia unlike other TM ions. Even colour can help, Mn7+ is usually purple, Mn2+ pink, Cu2+ blue etc. More sophisticated methods might include magnetic susceptibility to test for unpaired electrons, determining ligand field stabilisation energies etc. If you mean how is it determined from electronic configurations then it is easiest to consider the ground states of, say the first row TMs- Sc 4s2 3d1 Ti 4s2 3d2 V 4s2 3d3 Cr 4s1 3d5 Mn 4s2 3d5 Fe 4s2 3
