Question

calculate the unpaired electron in mn³+and fe³​

Answer 1

✪ 1) Mn$^{3+}$   ✪

The electronic configuration of Mn (atomic number 25) is:

1s$_2$ 2s$_2$ 2p$_6$ 3s$_2$ 3p$_6$ 4s$_2$ 3d$_5$

Now, since Mn is given +3 charge, 3 electrons will be removed.

Remember to remove electron always from the outer orbit first (Here, 4 is outer orbit.)

So, complete 4s$_2$ will be removed and one electron from3d will be removed. Thus, electronic configuration of Mn$^{3+}$ is:

1s$_2$ 2s$_2$ 2p$_6$ 3s$_2$ 3p$_6$  3d$_4$

As you can see,all orbitals apart from 3d are completely filled.

★ Hence, number of unpaired electron here is four. ★

✪  2) Fe$^{3+}$   ✪

Iron, having atomic number 26,its electronic configuration can also be written in similar manner.

1s$_2$ 2s$_2$ 2p$_6$ 3s$_2$ 3p$_6$ 4s$_2$ 3d$_6$

So, Fe$^{3+}$ can be written as:

1s$_2$ 2s$_2$ 2p$_6$ 3s$_2$ 3p$_6$ 3d$_5$ (removing 2 electron from 4s and one from 3d)

★ Thus, Number of unpaired electron is 5. ★