Some square planar complexes of Ni(II) are diamagnetic while some others are paramagnetic. Justify.

Explanation

In some complexes, the two unpaired 3d electrons pair up and the hybridisation is `dsp^(2)`. Thus, no unpaired electron is left. In some other complexes, one unpaired 3d electron is excited to 4p. Hybridisation is again `dsp^(2)` but there are two unpaired electrons present.