# Question #1b269

Sep 15, 2017

Here's why that is the case.

#### Explanation:

Your quantum number set cannot describe an electron in an atom because the value of the magnetic quantum number, ${m}_{l}$, is not permitted given the value of the angular momentum quantum number, $l$.

In your case, you have

$\left(\textcolor{red}{3} , \textcolor{b l u e}{2} , \textcolor{p u r p \le}{3} , - \frac{1}{2}\right)$

The electron is said to be located on the third energy level, which has $n = \textcolor{red}{3}$, in the $d$ subshell, which is denoted by

$l = \textcolor{b l u e}{2}$

For the $d$ subshell, the magnetic quantum number is restricted to a total of $5$ values

${m}_{l} = \left\{- 2 , - 1 , 0 , 1 , 2\right\}$

As you can see, ${m}_{l} = \textcolor{p u r p \le}{3}$ is not possible for an electron located in the $d$ subshell $\to$ this quantum nubmer set cannot describe an electron in an atom.