Question

In sodium, how many electrons in the ground state have the magnetic quantum number, $m=0$?

• A. $8$
• B. $7$
• C. $9$
• D. $6$

Answer 1

The correct option is B $7$

1 subshell in each orbital has $m=0$, which can house two electrons. The electronic configuration of sodium is:
$Na=1s^2,2s^2,2p^6,3s^1$
Here, $7e^{-}$ have m = 0 (2 each from $1s,2s,2p$ and $1$ from $3s$).