Question

An atom has a mass number of 31 and an atomic number of 15. How many protons and how many neutrons are in this atom? Show the nuclear symbol for this atom.

Answer 1

The atomic number of an atom is equal to the amount of protons the atom has, and the mass number is equal to the sum of the protons and neutrons. Therefore:

let protons = p
let neutrons = n                                                  
let atomic mass = a

P+N=A 
15+n=31
n=16

There are 16 neutrons in this atom.
(See attached for nuclear symbol)