To understand hybridization let’s take an example, [Co(NH3)6]3+Here it is clear that the coordination number of this complex is 6. So the complex must adopt octahedral geometry. The only thing we have to predict is whether it’s hybridization is sp3d2 ord2sp3
Steps to predict hybridization:
1. In the first step, we have to calculate the oxidation state of the metal ion. So the oxidation state of cobalt is +3.
2. Then predict whether the ligand is strong or weak and then according to this arrange electrons in the d-orbital.
3. If the ligand is strong, then pairing occurs from the initial condition(low spin complex) and if the ligand is weak then first all the d-orbital is singly filled and then pairing occur(High spin complex)
4. In the given example NH3 is a strong ligand so that it will form a low spin complex.
5. From the above picture, we can see that 6 vacant orbitals of metal ion combine with 6 NH3 ligands to give d2sp3 hybridization.
6. As the d-orbital present in the inner side, it is an inner orbital octahedral complex.
For more details follow this link
Hybridization in a coordination compound
High spin and low spin complex