Which of the following complexes have a maximum number of unpaired electrons?

CHEMISTRY · Single correct · A Level · Chemistry · Transition metals and their chemistry · Transition metals and their chemistry

Problem

Which of the following complexes have a maximum number of unpaired electrons? (1)

[\text{Ni}(\text{CO})_4]

(2)

[\text{Co}(\text{NH}_3)_4(\text{NO}_2)_2]^+

(3)

[\text{Ag}(\text{CN})_2]^-

(4)

[\text{CuBr}_4]^{2-}