Specify the oxidation numbers of metals in the following co-ordination entites :
(a) `[Co(H_(2)O)(CN)(en_(2))]^(2+)` (b) `[PtCI_(4)]^(2-)`
(c) `[Cr(NH_(3))_(3)CI_(3)]` (D) `[CoBr_(2)(en)_(2)]^(+)`
(e) `K_(3)[Fe(CN)_(6)]`.

Explanation

(a) O.N. Of Co : x + 0 + (-1) + 2 (0) = + 2 (0) = + 2 or x = + 2 + 1 = + 3
(b) O.N. Of Pt : x + 4 (-1) = -2 or x = -2 + 4 = + 2
(c) O.N. Of Cr : x + 3(0) + 3(-1) = 0 or x = + 3
(d) O.N. Of Co : x + 2(-1) + 2(0) = + 1 or x = + 1 + 2 = + 3
(e) O.N. of Fe : x + 6(-1) = - 3 or x = - 3 + 6 = + 3