Q. How many of the following has 4 unpaired electrons? $Cr^{2 +},Co^{3 +},Cu^{2 +},Ni^{2 +}$
NTA AbhyasNTA Abhyas 2022
Solution:
Ions Electronic configuration No. of unpaired electrons $Cr^{2 +}$ $\left[A r\right]3d^{4}$ $4$ $Co^{3 +}$ $\left[A r\right]3d^{6}$ $4$ $Cu^{2 +}$ $\left[A r\right]3d^{9}$ $1$ $Ni^{2 +}$ $\left[A r\right]3d^{8}$ $2$
| Ions | Electronic configuration | No. of unpaired electrons |
| $Cr^{2 +}$ | $\left[A r\right]3d^{4}$ | $4$ |
| $Co^{3 +}$ | $\left[A r\right]3d^{6}$ | $4$ |
| $Cu^{2 +}$ | $\left[A r\right]3d^{9}$ | $1$ |
| $Ni^{2 +}$ | $\left[A r\right]3d^{8}$ | $2$ |