Recently in my physics class we have been discussing the relationship between quantum numbers and the electron orbitals of the atom. After trying all day to understand this concept, Id like to post my misconception to the SNF community;

 

Here is my confusion: Electrons arrange themselves in orbitals and sub orbitals, and in the lowest orbital (s), they can be arranged (as in the first few elements):

H: 1s^1 (one electron in the 1s subshell)

He: 1s^2 (two electrons in the 1s subshell)

Li: 1s^2 2s^1 (two electrons in the 1s subshell and one in 2s)

 

this is where i cant seem to understand; how is it that there are now 3 electrons (and many more as the order continues, going to 3s and 4s) in the first orbital, when only 2 are supposed to be allowed [#of electrons = 2(2l+1)]?

?

 

2s2, thats shell two in the first part right, with the associated subshell for it. I think right, I mean there is no p, or d in hydrogen.

i think iv figured it out (thanks to a couple youtube videos)

 

the first orbital n=1 has no subshells, so 2 electrons fill the s shell. as for other orbitals the first two electrons fill the 1s subshell then start filling the s subshell of the n=2 orbital.

OK, for an atom there are four different quantum numbers that describe the electrons in the atom. These are

 

The principal quantum number, n

Orbital angluar momentum quantum number, l

Magnetic quantum number, ml

Magnetic spin number, ms

 

Now the principal quantum number n can take any value from 1 upto infinity.

 

The orbital QN, l, can take a value from 0 upto n-1 (where n is the principal QN)

 

The magnetic quantum number can have values from -l...0...l (where l is the orbital QN)

 

The magnetic spin number is either 1/2 or -1/2 (for electrons anyway)

 

 

The final thing you need to know is that two electron in the same atom can not have the same set of QN. So at the being, n=1 and so l=0, ml=0 and ms= +/- 0.5. This means that you can only but two electrons when n=1.

 

When n=2, l=0 and 1 so ml=-1, 0, 1. This allows you to have 8 electrons when n =2.

 

 

 

Hopefully thats helped....