Answer
(a) 4
(b) 4
Work Step by Step
(a) The number of ligand donor atoms directly bound to the metal ion is called its coordination number.
Ethylenediamine (en) ligand is bidentate, so each occupies two coordination sites. Therefore, coordination number= $2\times2=4$
(b) $C_{2}O_{4}$ is also a bidentate ligand so that each occupies two coordination sites. Therefore,
Coordination number= $2\times2=4$
