### Finding Quantum Numbers

Posted:

**Wed Oct 14, 2015 9:07 pm**How do you know what the m(l) quantum number for an element is?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=20&t=6289

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Posted: **Wed Oct 14, 2015 9:07 pm**

How do you know what the m(l) quantum number for an element is?

Posted: **Wed Oct 14, 2015 9:23 pm**

in order to find l, you must first know the principle quantum number (n) which is also the shell the electron exists in. From there, you can then find the angular momentum quantum number (l) which is equal to numbers ranging from 0 to n-1. Finally, the magnetic quantum number (m(l)) is equal to values l, l-1,...,-l.

Posted: **Wed Oct 14, 2015 9:35 pm**

n= principle quantum number, the shell the electron is in. For example, if an atom's electron configuration ends with 5s1, its n=5.

L=numbers from 0 to n-1. So for the example mentioned above, l can be 0, 1, 2, 3, or 4.

M_{l} = can be positive and negative possible l values. -4, -3, -2, -1, 0, 1, 2, 3, 4 in our example.

M_{s} = either -1/2 or 1/2. After drawing boxes of orbitals and filling in valence electrons, if the last electron is an upwards arrow in the diagram, Ms is 1/2. A downwards point is -1/2

L=numbers from 0 to n-1. So for the example mentioned above, l can be 0, 1, 2, 3, or 4.

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