# What are quantum numbers used to describe?

##### 1 Answer
Dec 7, 2014

Quantum numbers are used to describe an atom's electron distributions. Particularly, they represent acceptable solutions to Schrodinger's wave equations for the Hydrogen atom (more here: http://en.wikipedia.org/wiki/Schr%C3%B6dinger_equation )

There are $4$ quantum numbers: $n$, $l$, ${m}_{l}$, and ${m}_{s}$.

The quantum number that indicates the orbital is $l$. This quantum number varies from $0$ to $n - 1$ and idicates the s, p ,d or f subshell:

$l$= $0$ -> s subshell;
$l$ = $1$ -> p subshell;
$l$ = $2$ -> d subshell;
and so on.

Think of quantum numbers as forming a map to a certain electron's location, each electron having a distinct set of quantum numbers to describe its position.
For example, $n$=$2$, $l$=$1$, ${m}_{l}$=$0$, and ${m}_{s}$=$+ \frac{1}{2}$ correspond to one electron located on the second energy level, in one of the three $p$-orbitals (the one corresponding to ${m}_{l}$=$0$), that has a positive spin. Therefore, that electron would be located in $2 {p}_{y}$ ( $2 {p}_{x}$ would correspond to ${m}_{l}$ = $- 1$ and $2 {p}_{z}$ to ${m}_{l}$=$+ 1$ ) and have a positive spin.