If an atom has 15 protons and a mass of 31 how many neutrons will it have

16

Explanation:

To find the neutrons, it's always mass-atomic number. Since the atomic number for an atom is always the protons, it's really mass-protons.

31-15=16

let that person have a turn to speak : )

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.