For : Nickel (Ni) is in the 0 oxidation state. Its electronic configuration is . Carbonyl (CO) is a strong field ligand, causing pairing of electrons. The electrons are also pushed into the orbital, resulting in a configuration. The empty orbitals available for bonding are one and three orbitals, leading to hybridization (tetrahedral geometry). Thus, C IV.
For : Platinum (Pt) is in the oxidation state (). has a electronic configuration. For 5d series elements, even weak field ligands like chloride () cause electron pairing. The configuration with pairing leads to one empty orbital, one orbital, and two orbitals for hybridization, resulting in hybridization (square planar geometry). Thus, D I.
💡 Teacher's Secret HintRemember that ligand field effects (strong vs. weak field ligands) are crucial for determining hybridization in coordination compounds, especially for transition metals.