Question

The four quantum numbers for the valence shell electron of sodium (Z = 11) is ___________.

• A. $n=2,l=1,m=-1,s=+\frac{1}{2}$
• B. $n=3,l=0,m=0,s=+\frac{1}{2}$
• C. $n=3,l=2,m=-2,s=-\frac{1}{2}$
• D. $n=3,l=2,m=2,s=+\frac{1}{2}$

Answer 1

The correct option is B $n=3,l=0,m=0,s=+\frac{1}{2}$

Each electron in an atom is described by a set of four quantum numbers $\text{n}$, $\text{l}$, ${\text{m}}_{\text{l}}$ and ${\text{m}}_{\text{s}}$.

The electronic configuration of sodium is $1s^{2}2s^{2}2p^{6}3s^1$ and the last electron of the sodium atom is represented as $3s^1$.

It is in the third shell and 's' sub-shell, hence, the value of $\text{n}$ = 3 and $\text{l}$ = 0.

Since $\text{l}$ = 0, ${\text{m}}_{\text{l}}$ is also 0 and the spin of an electron could be either +1/2 or -1/2.

Hence, the correct set of quantum numbers is $n=3,l=0,m=0,s=+\frac{1}{2}$.