Question

What is the oxidation states of cobalt in each of the following and include dn electronic configuration for these compouds:

1) [Co(H₂O)₆]²⁺

2) [Co(NH₃)₆]²⁺

3) CoCl₃.5NH₃

4) CoCl2.6H₂O

Answer 1

Answer:

By considering rules for oxidation states

1. [Co(H₂O)₆]²⁺

Oxidation state of cobalt in above compound is +2

Explaination :

Let oxidation state of cobalt be x

oxidation state of O is -2 and oxidation state of H is +1 (so H₂ = +2) so net charge of H₂O is +2 -2=0

Net charge of above complex compound is +2

so put all values of charges in compound

i.e x + 0(6) = +2

x= +2 - 0

x= 2

so oxidation state of cobalt in above compound is +2

electronic configuration of [Co(H₂O)₆]²⁺ is d²sp³

Explaination:

electronic configuration of Co = (Ar) 3d7 4s2 (so valence electron of Co (s-orbital of Co) is +2)

H = 1s (so valence electron of H (s-orbital of H) is 0)

O =1s2 2s2 2p4 (so valence electron of O (s-orbital of O) is +6)

Charge on compound is +2

So put the values in above compound

i.e 2 +(12)6+66-2

so 2+ 12 + 36 -2

=48 total elecrons,

divided the total electrons by valence electron i,e 8

i.e 48/8

=6 (no of orbitals)

i.e (1s + 3p + 2d) orbitals

so electronic configuration is d²sp³

2. [Co(NH₃)₆]²⁺

Oxidation state of cobalt in above compound is +2

Explaination :

Let oxidation state of cobalt be x

oxidation state of N is -3 and oxidation state of H is +1 (so H3 = +3) so net charge of NH3 is -3+3=0

Net charge of above complex compound is +2

so put all values of charges in compound

i.e x + 0(6) = +2

x= +2 - 0

x= 2

so oxidation state of cobalt in above compound is +2

electronic configuration of [Co(NH₃)₆]²⁺ is d²sp³

3. CoCl₃.5NH₃

Oxidation state of cobalt in above compound is +3

Explaination :

Let oxidation state of cobalt be x

oxidation state of Cl is -1

oxidation state of N is -3 and oxidation state of H is +1 (so H3 = +3) so net charge of NH3 is -3+3=0

so put all values of charges in compound

i.e x + (-1)3 +5 (0)

x= +3

so oxidation state of cobalt in above compound is +3

4. CoCl₂.6H₂O

Oxidation state of cobalt in above compound is +2

Explaination :

Let oxidation state of cobalt be x

oxidation state of Cl is -1

oxidation state of O is -2 and oxidation state of H is +1 (so H₂ = +2) so net charge of H₂O is +2 -2=0

so put all values of charges in compound

i.e x + (-1)2 +6 (0)

i.e x-2+0

so x= +2

so oxidation state of cobalt in above compound is +2