Question

An element has $13$ electrons in its $M$ shell and electron in $N$ shell in ground state. Identify the element.

• A. Chromium
• B. Iron
• C. Manganese
• D. Copper

Answer 1

Answer: (A)

M shell means it is third shell
$\Rightarrow n=3$
Number of electrons in $M$ shell=13
$\Rightarrow 3s^{2}3p^{6}3d^5$
and $N$ shell means it is fourth shell
$\Rightarrow n=4$
Number of electrons in $N$ shell $=1$
$4s^1$
thus the electronic configuration is:
$\left(1s^2\right)\left(2s^{2}2p^6\right)\left(3s^{2}3p^{6}3d^5\right)\left(4s^1\right)$
The element is Chromium $(Cr)$