## Angular Momentum Quantum Numbers

Schem_student
Posts: 29
Joined: Fri Sep 28, 2018 12:19 am

### Angular Momentum Quantum Numbers

When I was going through the quantum world problem section I was confused about using l=n-1 but if we were given 5d then l= 2 not l=5-1which would gove you l=4. Why is it always l=2 for d subshell even when we are in the shell n=5?

Andrew Sun 1I
Posts: 30
Joined: Fri Sep 28, 2018 12:18 am

### Re: Angular Momentum Quantum Numbers

quantum number for l just describes the shape. It isnt necessarily always going to be l=n-1. For example, the third energy level has s, p, and d orbitals, meaning you can have l=0,1 or 2 for which electron you are describing.

Clarissa Cabil 1I
Posts: 66
Joined: Fri Sep 28, 2018 12:19 am

### Re: Angular Momentum Quantum Numbers

n denotes the possible orbits/energy levels/shells we can have.
n can range from 1, 2, 3, 4, 5, etc.
If n = 5, the possible l values are 0, 1, 2, 3, and 4 because l = 0, 1, 2, ... (n-1).
However, since it is specified in the problem that we are in the d orbital, l MUST equal 2 (since l=0 for s, l=1 for p, l=2 for d, l=3 for f, and l=4 for g).

If the problem only said that n=5, l could have been 4. But since we were given a specific orbital, we can determine the actual value for l in this situation.

Hope this helps!

A De Castro 14B 2H
Posts: 75
Joined: Fri Sep 28, 2018 12:29 am

### Re: Angular Momentum Quantum Numbers

The "l=n-1" indicates that the shell (principal quantum number, n) limits the number of subshells (angular momentum quantum number, l) that can be inside it. Say n=2, thus the only possible l values are 0 and 1, which further means that the only subshells within the n=2 shell are s and p respectively.