The atomic numbers of elements `X,Y`,and `Z` are `19,21`, and `23`, respectively. The number of eletron present in the `M` shells of these elements follows the order

Options

A. `Z gt X gt Y`
B. `X gt Y gt Z`
C. `X gt Y gt Z`
D. `Z gt Y gt X`

Answer

C

Explanation

`X^(19) : underset(K) (1s^(2)) underset(L)(2s^(2) 2p^(6)) underset(M)(3s^(2) 3p^(6)) underset(N)(4s^(1))`
`Y^(21) : underset(K) (1s^(2)) underset(L)(2s^(2) 2p^(6)) underset(M)(3s^(2) 3p^(6)) 3d^(1)underset(N)(4s^(1))`
`Z^(25) : underset(K) (1s^(2)) underset(L)(2s^(2) 2p^(6)) underset(M)(3s^(2) 3p^(6)) 3d^(5) underset(N)(4s^(1))`
Electrons in M shell of these elements are
`Z^(25) (13) gt Y^(21) (9) gt X^(19) (8)`