Question

What are the oxidation states and d-electron counts for the metal ions?

a)CoCl3(NH3)3

b) NiCl42-

c)K4Fe(CN)6

Answer 1

a). CoCl3(NH3)

Oxidation state:

Cl has -1 oxidation state . NH3 does not have any charge on it. So the oxidation state of Co depends on Cl only

3Cl = -3 so Co must have +3 oxidation state

Electronic configuration of Co is [Ar] 3d7 4s2

When oxidation state of Co is +3 this means that its 2 s and 1 electrons of d is removed so there are 6 electrons remained in d orbital.

b). NiCl4 2-

lets assume oxidation state of Ni is x then

x + 4 (-1) = -2  

here -1 is oxidation state of Cl and -2 is the charge on it.

x -4 = -2

x = +2

so oxidation state of Ni is +2

electronic configuration of Ni is [Ar] 3d8 4s2

when its oxidation state is +2 then its 2 electrons from 4s are removed and then there are 8 d electrons.

c)

K4Fe(CN)6

There is -1 charge on CN

+1 charge on K

Therefore Fe should have +2 oxidation state since -6 charge on CN is balanced by 4K and 1 Fe

So Fe is having +2 oxidation state.

Electronic configuration of Fe is [Ar] 3d6 4s2

2 electrons are removed so there are 6 d electrons in Fe.