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### Quantum Numbers

Posted: **Sun Nov 03, 2019 10:49 pm**

by **605357751**

I have difficulty understanding the rules of quantum numbers, can someone explain why some combinations are allowed and others are not.

State if the following combinations of quantum numbers are allowed or not in a one-electron

atom. For those that are disallowed state briefly why not.

a) n = 4, l = 3, ml = -4, ms = 0

b) n = 3, l = 3, ml = 1, ms = -1/2

c) n = 5, l = 2, ml = -3, ms = +1/2

### Re: Quantum Numbers

Posted: **Sun Nov 03, 2019 10:51 pm**

by **AndreiRekesh1I**

IIRC l must be at most one fewer than n in all cases, and the absolute value of ml must be at most equal to l.

### Re: Quantum Numbers

Posted: **Sun Nov 03, 2019 10:55 pm**

by **zachary_nhem_4I**

There are some energy levels that don't have certain orbitals. For example, for part b, the f block (l=3) exists within the 6th energy level (n=6), as a result, n = 3, l = 3, ml = 1, ms = -1/2 does not exist.

### Re: Quantum Numbers

Posted: **Sun Nov 03, 2019 11:02 pm**

by **Julie Park 1G**

ms (spin quantum number) describes the magnitude and direction that an electrons spins

ms only has two possible values: +1/2 and -1/2

therefore, there is no such thing as ms = 0

### Re: Quantum Numbers

Posted: **Tue Nov 05, 2019 11:02 pm**

by **Kennedi2J**

There was also a question: How many electrons can have the following quantum numbers in an atom?

a) n=5, l=3, ml= -1 and the answer was 2 electrons

Can anyone explain why the answer is 2 electrons and not 14 since l corresponds to f orbital and f orbital can hold 14 electrons?