# Homework Help: Quantum numbers problem

1. Nov 28, 2011

### fluidistic

1. The problem statement, all variables and given/known data
List all possible values for the quantum numbers $n$, $l$, $m_l$ and $m_s$ for a state 2p. If an atom has 2 electrons 2p, how many states are there?

2. Relevant equations
Simple ones.

3. The attempt at a solution
$n=2$.
$l=1$.
$m_l=-1, 0, 1$.
$m_s=-1/2, 1/2$.
Now I'm confused on how to answer the question.
2 electrons in 2p means 2 electrons with quantum numbers:
(n,l,m_l,m_s)=
(2,1,-1,1/2) and (2,1,-1,-1/2)
or (2,1,-1,-1/2) and (2,1,-1,-1/2)
or (2,1,-1,1/2) and (2,1,0,1/2)
or (2,1,-1,1/2) and (2,1,0,-1/2)
or (2,1,0,1/2) and (2,1,-1,1/2)
or etc.
I mean an electron can have a certain $m_l$ while the other can have any other $m_l$ incuding the same $m_l$ as the first electron. When they have the same m_l, they must have opposite spin. Is this ok?

2. Nov 29, 2011

### dextercioby

Yes, the only requirement is that the electrons must not have the same quantum numbers. If 3 of them are identical, the 4th is forced to have different values among them.

3. Nov 29, 2011

### fluidistic

Ok thank you.