Atomic mass of suphur is not a whole number. It is 32.06 amu or u. There are 16 protons and 16 neutrons. There are other isotopes with 17, 18, 19, 20 neutrons in the nucleus of sulphur. The atomic mass shown is the average of the mixture of all isotopes taking into account their relative proportions.
atomic mass of chlorine is 35.45, it has 17 protons in one isotope and 18 neutrons in another isotope. The mixture has an average atomic weight of 35.45, taking into account the relative proportions of the isotopes. Perhaps there is one more isotope of 19 neutrons with 17 protons.