In an atom, the total number of electrons having quantum numbers
`n = 4,|m_(l)| = 1` and `m_(s) =- (1)/(2)` is

Answer

6

Explanation

When `n = 4, l = 0, 1, 2, 3`
When `l = 0, m = 0`
When `l = 1, m = -1, 0, + 1`
(Two p-orbitals have `|m| = 1`)
When `l = 1, m = -2, -1, 0 + 1, +2`
(Two d-orbitals have `|m| = 1`)
when `l = 3, m = -3, -2, -1, 0 , + 1, + 2, +3`
(Two f-orbitals have `|m| =1`)
Thus, `|m_(1)| =1` for two p, two d and two f-orbitals.
Each of these orbitals has only one electron with `m_(s) = - (1)/(2)`. Hence, total number of electrons = 6