Electron Configurations Electron configurations are the very foundation of understanding all of the elements in the periodic table, and in fact the shape of the periodic table is based on the electron configurations. For this lecture, I am only using the periodic table under the Resources page. Each sub-shell of the atom is expressed in the electron configuration. The outer valence electrons would be the last electrons in the electron configuration for a particular atom. Each sub-shell in the electron configuration has the form Nl#where N is the primary quantum number and will range from 1 to 7, lis the sub-shell shape and will be either s, p, d, or f, and the # represents the number of electrons in that sub-shell. An s sub-shell can only hold up to 2 electrons, a p sub-shell can hold up to 6 electrons, a d sub-shell can hold up to a maximum of 10 electrons, and an f sub-shell can hold up to a maximum of 14 electrons. You do not have to memorize the latter maximums because the periodic table lays it all out for you. You will notice that the periodic table has four distinct regions. Each region represents the sub-shell shape and thus the lsymbol, as shown:
You can see that the s orbital only has two columns, thus a maximum of 2 electrons can be held in an s orbital. A p orbital only has six electrons, thus a p sub-shell can only hold a maximum of 6 electrons, as so on for the d and f orbitals. Also notice that I moved the element, He, over to the s orbital for doing electron configurations. Keep that in mind when doing the electron configuration of He.
- Fall '19
- Periodic Table, Electron shell, Valence electron, 1s22s22p63s23p