Why Do Electron Shell Capacities Differ Between GCSE and AS Level?

[MattA147]

Electronic Structure question? :)

Hey guys essentially in my GCSE Chem class we were told that the maximum number of electrons that can be held in the first four shells are as follows - 2,8,8,2. Now in my AS Level textbook it is saying that it goes 2,8,18,32. Can someone please explain to me why this is the case, and give me some clarification?

 

[Infinitum]

Hi Matt!

The maximum possible electrons in the shells are 2,8,18,32... given by 2^n, where n is the principal quantum number. But there also is another condition that the valence shell must have 8 electrons or less, because that is how we define valency to be less than 8.

You might want to take a look at this page : http://en.wikipedia.org/wiki/Electron_shell#List_of_elements_with_electrons_per_shell

 

[MattA147]

Thanks for your reply, that article is making a lot more sense than any other article I found. It is appreciated. :)