Revise GCSE Physics

Question:What is the mass number for an atom?

The mass number of an atom, tells us how many protons and neutrons are present in the nucleus of that atom.

The mass number equals the number of protons plus the number of neutrons in the nucleus.

You can calculate the number of neutrons in the atoms nucleus by taking the atomic number away from the mass number.

Number of neutrons = mass number - atomic number