It has to do with the order in which the subshells fill; i.e., after 18 electrons are in the 4th shell, (that's the 1s2(K shell 2) 2s2 2p6(Lshell 8) 3s2 3p6 3d10(M shell 18) 4s2 4p6 4d10(N shell 18) 5s2 5p5), the 5s and 5p subshells are lower energy and fill next. Here is a diagram from Wikipedia that shows how the filling takes place.
http://en.wikipedia.org/wiki/Electron_configuration#/media/File:Electron_orbitals.svg
Hi,
Iodine has 53 electrons and configuration of: 2, 8, 18, 18, 7.
Why does the fourth shell not reach maximum and therefore it picks up 7 electrons and begins a new shell.
Thank you.
1 answer
1 answer