To write an electron configuration, its just how many electrons are in each shell. See, Sulfur has 3 shells. The first shell has 2 electrons, The second shell has 8 electrons. The third shell has 6 electrons. So the lectron configuration of Sulfur would be 2-8-6. The first shell can have no more than 2 electrons and the second shell can have no more than 8 shells, that is why Sulfur has 3 shells.
