Question

The correct set of four quantum numbers for the outermost electron of sodium ($Z=11$) is :

• A. $3,1,0,\frac{1}{2}$
• B. $3,1,1,\frac{1}{2}$
• C. $3,2,1,\frac{1}{2}$
• D. $3,0,0,\frac{1}{2}$

Answer 1

Answer: (D)

$3,0,0,\frac{1}{2}$

The correct set of four quantum numbers for the outermost electron of sodium ($Z=11$) is $3,0,0,\frac{1}{2}$
The electronic configuration of $Na$ is $1s^{2}2s^{2}2p^{6}3s^1$. Thus, the last electron is in $3s$ sub-shell.
For $3s$ sub-shell, $n=3$,
$l=0$, $m=0$ and $s=\pm \frac{1}{2}$