The maximum number of electrons that can have principal quantum number `n=4` and spin quantum number `m_(s)=-(1)/(2)` is:

Answer

9

Explanation

Number of electrons will (n=3)`=2n^(2)=18`. Half of these electrons will have anticlockwise spin, i.e., `m_(s)=-(1)/(2)` i.e., 9 electrons.