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

Options

A. `+2`
B. `+3`
C. `Both +2 and +3`
D. `-1`

Answer

C

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
Structure is `3d^(4),4s^(2)`
So `e^(bar)` can be excited from `4s` and `3d` both (since energy difference between `3d` and `4s` very very small ) So, veloncy is `+ 2` and `+3` both