Question

How many neutrons are in an atom of sulfur with a mass number of 35?
a. 16
b. 17
c. 18
d. 19

Answer 1

As the mass difference between protons and neutrons isn't too different we can determine how many neutrons an atom has by subtracting the number of protons from its atomic mass.

Sulfur has 16 protons, so 35-16 = 19. So there are 19 neutrons present.