First, we'll calculate the valency of chlorine by using the net charge on the ClO₄ ion. The ClO₄ ion has a charge of -1, while each oxygen atom exhibits a charge of -2. Therefore,
Cl + 4(-2) = -1 Cl = 7
Next, the valency of Mn is calculated by using the overall charge, which is 0
Mn + 3(-1) = 0 Mn = 3
Therefore, the valencies are: Mn = 3 Cl = 7 O = -2