Complex salt has two parts-one is ionisation sphere and another is coordination sphere. According to IUPAC nomenclature of complex, first we name positive ion then negative ion. According to VBT, metal ion should have vacent orbital equal to its coordination number. If ligand is strong field, pairing of electrons takes place. In the case of weak field ligand, pairing of electrons does not take place, generally. Crystal field splitting of d-orbitals of tetrahedral complex is just opposite to that octahedral complex.
A. `[Ni(CO)_(4)]`
B. `[Pd(NH_(3))_(4)]Cl_(2)`
C. `[Fe(CO)_(5)]`
D. `K_(2)[ZnCl_(4)]`
