Write the structure and the hybridisation of the central atom in `[Ni(CO)_4]`

Explanation

Ni in ground-state has electronic configuration of [Ar] `3d^8. 4s^2`. When CO, a strong ligand approaches the metal atom, it causes pairuig of 4s-electrons in the 3d-orbitals. The four (one 4s and three 4p) empty orbitals get hybridised (`sp^3`). The complex has a tetrahedral shape. Since no unpaired electron is present, therefore, the complex is diamagnetic.