Chapter 24 - Sections 24.1-24.6 - Exercises - Problems by Topic - Page 1125: 21b

Oxidation state= +2 Coordination number= 4

Let the oxidation state of the metal ion be $X$. Then, $X+4(-1)=-2$ $\implies X=+2$ The number of ligands directly bound to the metal ion is called the coordination number. Therefore, coordination number, in this case is equal to 4.