In the tetrahedral complex $K_2[NiCl_4]$,what is the number of electrons present in the $3d$ orbital of the central metal ion?

In the crystal of $CuSO_4 \cdot 5H_2O$,the copper atom is coordinated by:

According to $V.B.T.$,in which of the following complexes does the transition of an electron occur from one shell to another shell of the central metal atom?

When $(n-1)d$ orbitals participate in the hybridization of a coordination complex,the resulting complex is known as:

Assertion $:$ Complex ion $[Co(NH_3)_6]^{2+}$ is readily oxidized to $[Co(NH_3)_6]^{3+}$.
Reason $:$ Unpaired electron in complex ion $[Co(NH_3)_6]^{2+}$ is present in $4p$ orbital.

Select the incorrect match.