Question

A neutral atom of an element has 2K, 8L, 9M and 2N electrons
The total number of unpaired electrons are :

• A. $1$
• B. $2$
• C. $3$
• D. $4$

Answer 1

The correct option is A $1$

A neutral atom of an element has 2K, 8L, 9M and 2N electrons so it have total electrons of 21.
so it has 21 proton and its atomic no is 21.
and electronic configuration of element is
$1s^{2}2s^2{p}^{6}3s^2{p}^6{d}^{1}4s^2$
so no of unpaired electrons are 1.