Sulfur has 16 electrons. With 16 electrons you will have 3 shells with 2, 8 and 6 on each shell. Having 6 electrons on the last shell, it will have 2 subshells, the s subshell and p subshells with 2 and 4 electrons respectively. The lowest energy peak subshell for which the electron can be emitted is the p subshell of the third shell.