Calculating numbersHere, we'll look at some examples of different elements.
We'll look at how you can use the atomic number and mass number to calculate the number of sub-atomic particles in their atoms.
Select each element to find out more
Hydrogen has an atomic number of 1 and a mass number of 1. This means a hydrogen atom has:
- 1 proton ( = atomic number)
- 1 electron ( = atomic number)
- 0 neutrons (mass number - atomic number, 1 - 1 = 0)
Helium has an atomic number of 2 and a mass number of 4. This means a helium atom has:
- 2 protons ( = atomic number)
- 2 electrons ( = atomic number)
- 2 neutrons (mass number - atomic number, 4 - 2 = 2)
The gas nitrogen has an atomic number of 7 and a mass number of 14. This means a nitrogen atom has:
- 7 protons ( = atomic number)
- 7 electrons ( = atomic number)
- 7 neutrons (mass number - atomic number, 14 - 7 = 7)
Iron has an atomic number of 26 and a mass number of 56.
This means an iron atom has:
- 26 protons ( = atomic number)
- 26 electrons ( = atomic number)
- 30 neutrons (mass number - atomic number, 56 - 26 = 30)
