Write down electronic configuration of `Fe^(3+)` ion and anwer the following:
(i) What is the number of electrons having `n+l=3` in it?
(ii) How many electrons in it have `n=3` and `m=0`?
(iii) How many electrons in it have `l=1`?
What is the number of electrons in M-shell?

Answer

`Fe^(+3)=1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(5)`
(i) `2p` and `3s` have `n+l=3` so number of electrons `=8`.
(ii) It is `III^(rd)` shell which contains three orbitals having `m=0` so number of electrons `=5`
(iii) It is `p` sub shell so number of electron `=12`
(iv) For M-shell `n=3` so number of electron `=13`