* Mass Number: The mass number represents the total number of protons and neutrons in an atom's nucleus.

* Atomic Number: Sulfur's atomic number is 16, which means it has 16 protons.

Calculation:

* Mass Number - Atomic Number = Number of Neutrons

* 35 - 16 = 19

Answer: There are 19 neutrons in an atom of sulfur with a mass number of 35.