Question

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

• A. 6
• B. 7
• C. 8
• D. 9

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 $3s$).