An aqueous solution of NiCl₂ was heated with excess sodium cyanide in presence of strong oxidizing agent to form [Ni(CN)₆]^2$$-$$. The total change in number of unpaired electrons on metal centre is _______________.

The spin-only magnetic moment value for the complex [Co(CN)₆]^4$$-$$ is __________ BM.

[At. no. of Co = 27]

The total number of unpaired electrons present in the complex K₃[Cr(oxalate)₃] is _____________.

On complete reaction of FeCl₃ with oxalic acid in aqueous solution containing KOH, resulted in the formation of product A. The secondary valency of Fe in the product A is __________. (Round off to the Nearest Integer).