Question

Which of the following quantum numbers are correct for the outermost electron of sodium atom?

• A. $n = 4$, $l = 0$, $m = 0$, $s = +1/2$
• B. $n = 3$, $l = 0$, $m = 0$, $s = -1/2$
• C. $n = 3$, $l = 1$, $m = +1$, $s = +1/2$
• D. $n = 3$, $l = 2$, $m = -1$, $s = -1/2$

Answer 1

Answer: (B)

For sodium atom: atomic number $=11$
thus its electronic configuration: $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{1}$
Outer most electron is in $3 s$ orbital and has quantum numbers as:
$n =3, l = s =0, m _{ l }=0, m _{ s }=+1 / 2$ or $-1 / 2$