Organic Chemistry

Coordination number is the number o dligands in the coordination sphere. Hence, the coordination number of cobalt ion in [Co(H2​O)4​SO3​]Cl  is 5.

Let the oxidation number of  Co is x.

x+4(0)+(−2)+(−1)=0

x+0−2−1=0

x=3

The number of electrons in d-orbital is six.

Number of unpaired electrons in d-orbital is 4 because of H2​O is a weak ligand and therefore, pairing of d-electrons in d-orbital is not possible.