# Question #39125

Jun 9, 2017

Because M shell has the capacity for $8$ electrons. Secondly, $18$
is used for all the sub shells in the M shell.

#### Explanation:

M shell has the capacity to store $8$ electrons.
We have divided $18$ in three sub shells of the shell M ,e.g.,
$3 s = 2$
$3 p = 6$
$3 d = 10$
$2 + 6 + 10$ = $18$
Electronic configuration of $C a$ =
$1 {s}^{2} , 2 {s}^{2} , 2 {p}^{6} , 3 {s}^{2} , 3 {p}^{6} , 4 {s}^{2}$, where;
$K = 2$
$L = 8$
$M = 8$
$N = 2$
You can take $18$ as a whole but, if you'll take the M shell it contains 8 electrons, if we'll also count its sub shell electro configuration then it will be greater than 8.