Basic question about energy levels

[DropBoite]

Hi all,

In case you haven't seen my previous post, I'm doing the IB syllabus for an entrance after a gap of 2 years so there's much I've forgotten, so please tolerate my noob-ness

I don't understand how an energy level which is said to have a max number of 8 electrons (ref. 10th grade chem) can accommodate sub-orbitals with more (ref 2n²). I am certain I've forgotten a fundamental that explains this, what's the explanation? Thanks!

[Garrett !?]

Do you mean electron configuration? It goes across the periodic table starting from Hydrogen and going down by period. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶

[emmapatregnani]

The only every level that has a max of 8 electrons is the second one. It has 2s2 and sp6, adding up to 8. Are you asking how can this energy level have more than 8 electrons?

[DropBoite]

No, actually what I'm talking about is the basic energy levels model we studied back in grade ten which had us writing stuff like 2,8,81 etc. In IB we learn configurations with suborbitals etc. So I was trying to understand where the latter fits in with the former. Is this clearer? Thank you

[Emmi]

That's essentially the same thing, but instead of listing out how many electrons are in which specific orbital (s, p, d, or f) you're just giving the total number of electrons in the entire energy level. You know the first energy level contains 2 electrons total, the second energy level contains 8 total, and so forth. It's assumed that you're going to fill up the s orbital first, then the p orbital, and then the d orbital (in transition-row elements, you actually will fill d before p).

For the example you gave, 2,8,8,1, this corresponds to an element in the fourth energy level because you've listed four different numbers. You have a complete first energy level (given by 2), a complete second energy level (given by 8), a complete third energy level (given by the second 8), and now you're beginning to fill the fourth energy level. The fourth level has only one electron in it (given by the 1) and you know you're filling the s orbital up because s is filled first. To find this element on the periodic table, you would start at the fourth energy level and go across until you reach that number of electrons. Since it's only one, this corresponds to potassium.

[DropBoite]

Configurations have the ability to hold more than 8 electrons per energy level, The basic model doesn't .

eg. n= 3, basic model total number of electrons = 8 e-

n=3 configuration possible is 3s, 3p, 3d which add up to a capacity of 18 e-!

I hope you'll get me now, this probably a ridiculous fundamental I've forgotten in the last two years. Sorry for the inconvenience, I appreciate that everyone is trying

Edited April 24, 2014 by DropBoite

[JonR]

Yes it does. Take xenon for example:

The basic model should give you 2, 8, 18, 18, 8

The actual electron configuration is (Kr) 5s2, 4d10, 5p6

[DropBoite]

Yes it does. Take xenon for example:

The basic model should give you 2, 8, 18, 18, 8

The actual electron configuration is (Kr) 5s2, 4d10, 5p6

That makes sense up until the second 18 which doesn't hold true because the 4th energy level has access to an f sub orbital which will excess this figures. Gosh this is lost cause.

[JonR]

It's because 5s and 5p are 'more accessible' than 4f, which is illustrated by the diagram below. The energy levels are not filled up chronologically, which also explains the octet rule.

However, this is due to the sub-orbitals, so the basic model does not offer any explanation for this. If you want to understand how this stuff works, my advice would be getting a good grasp on the workings of electron configurations. Translating it to the basic model won't be a problem.