Question

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

• A. $1$
• B. $42$
• 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 have 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 d electrons are 1.