A natural atom of an element has `2K,8L, 9M` and `2N` electrons .The atomic number of element is :
The total number of s electons are

Options

A. 8
B. 6
C. 4
D. 10

Answer

B

Explanation

`overset(2K,8L,9M,and,2N)underset(1s^(2),2s^(2)p^(6),3s^(2)3p^(6)3d^(1), 4s^(2))`
`({:(K means n = 1, l means n = 2),(M means n = 3 , N means n = 4):})`
`"Structure is" `3d^(1),4s^(2)`
Atomic number 21
`1s^(2) + 2s^(2) + 3s^(2) + 4s^(2) = 8`