[NiCl₄]²⁻ is paramagnetic due to the presence of two unpaired electrons in the nickel ion, which has the electronic configuration 3d⁸ in the +2 oxidation state.

In tetrahedral complexes, one s and three p orbitals undergo hybridization to form four equivalent orbitals arranged tetrahedrally. This hybridization is demonstrated in [NiCl₄]²⁻, where nickel is in the +2 oxidation state.

[Co(NH₃)₆]³⁺ is an inner orbital or low spin complex, using the inner d orbital (3d) in hybridization, while the paramagnetic complex [CoF₆]³⁻ is an outer orbital or high spin complex, utilizing the outer d orbital (4d) in hybridization.

The complex utilizes inner orbital (3d) hybridization, forming six pairs of electrons from NH₃ ligands in octahedral geometry, resulting in diamagnetism due to the absence of unpaired electrons.

The magnetic behavior of a complex can provide insights into its geometry; for example, diamagnetic complexes like [Co(NH₃)₆]³⁺ suggest octahedral geometry due to the absence of unpaired electrons.