## HW 2.29 [ENDORSED]

Maya Khoury
Posts: 29
Joined: Fri Apr 06, 2018 11:03 am

### HW 2.29

2.29 asks How many electrons can have the following quantum numbers in an atom:
(a) n = 2, l = 1
(b) n = 4, l = 2, ml = -2
(c) n = 2
(d) n = 3, l = 2, ml = +1

So I understand that for (a) there can be 6 electrons and for (c) there can be 8 electrons, but I don't fully understand why there can be 2 electrons for (b) and (d).
Essentially my question is how does the value for ml impact the number of electrons in an atom?

Thank you! sorry if this is a stupid question lol

Samantha Draghi 1L
Posts: 24
Joined: Fri Apr 06, 2018 11:02 am

### Re: HW 2.29  [ENDORSED]

No two electrons in an atom can have the same quantum numbers so therefore in b and d the only electrons that can have the same n, l, and ml would be if the electron is either spin up or spin down giving us only 2 options for electrons. On the other hand in something like A they could have those quantum numbers with ml= 0,1, or 2 each with either + or - 1/2 for spin giving us a possible 6 electrons.

Patience Olsen 1A
Posts: 28
Joined: Fri Apr 06, 2018 11:04 am

### Re: HW 2.29

The Pauli Exclusion Principle states that no two electrons in an atom can have the same four quantum numbers. Since in b) and d), ml is given, we know there can only be two electrons described by these numbers (one with ms=+1/2 and one with ms=-1/2).
So the value of ml doesn't actually matter. It's just the fact that we're given an ml which tells us that there are only two electrons possible.

vivianndo_1L
Posts: 30
Joined: Fri Apr 06, 2018 11:02 am

### Re: HW 2.29

I understand why a = 6 electrons and why b/d = 2 electrons, but why is c = 8 electrons?

RubyLake1F
Posts: 41
Joined: Fri Apr 06, 2018 11:03 am

### Re: HW 2.29

C=8 because the only quantum number that is specified is n=2, so you know it is in the second shell which has both an s sub shell and a p sub shell. The s sub shell has one orbital, so can hold 2 e-, and the p sub shell has 3 orbitals so it can hold 6 total e-. This gives a total of 8 electrons possible in the shell n=2. This makes sense if you look at the periodic table and see that in the second row there are 8 elements.