- Atomic mass is determined by the sum of protons and neutrons numbers in an atom
- Protons are a kind of subatomic particle
- Neutrons are a kind of subatomic particle
- So, atomic mass is determined by the sum of protons and neutrons particle numbers

Therefore, atomic mass is determined by the sum of protons and neutrons particle numbers
[Question]A student needs to find the mass of an atom. The numbers of which atomic particles determines the mass of the atom?
[Context]- Atomic mass is determined by the sum of protons and neutrons numbers in an atom 
- Protons are a kind of subatomic particle 
- Neutrons are a kind of subatomic particle