-8
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p
The order for filling in the sublevels becomes; 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d,7p.
This is best explained by an example: The electron configuration of Strontium (Sr) is: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 This can be simplified by using the noble gas that covers the most items. In this case it is Krypton (Kr) which has an electron configuration of: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 Do you see the similarity in the two configurations? This means that you can use [Kr] to represent 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 So the short-handed (simplified) way of writing Strontium is: [Kr] 5s^2 Everything before the 5s^2 was replaced with [Kr] Note: The "^" symbol means the the following number is in the form of a superscript.
argon is because it's the last noble gas used to get to Br.. it's like a short cut, instead of writing 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^5 you can skip a lot of it by taking th last noble gas used which is the 3p^6(Ar) and continue from there like so: [Ar] 4s^2 3d^10 4p^5
4p+2 = 3p-7 4p-3p = -7-2 p = -9
Up to 4p, the energy levels go as follows: 1s 2s 2p 3s 3p 4s 3d 4p
simply add the like terms: 4p -3p +2q -2q = p
1s 2s 2p 2p 2p 3s 3p 3p 3p 4s 3d 3d 3d 3d 3d 4p
1s 2s 3s 3p 4s 3d 4p
4p+7q
4p + 9 + (-7p) + 2 = 4p - 7p + 9 + 2 = -3p + 11
6
6
11-3p
4p+9-7p+2 -3p+11 p = 11/3
3p+5+p = -23 3p+p = -23-5 4p = -28 p = -7