Question

What are atoms of the same element that differ in the number of neutrons they contain called?

Answer 1

These are called `"isotopes"`.

Explanation:

Atoms of the same element were specified. If this were the case, then all the atoms have the same `Z`, i.e. atomic number, which is the number of massive, positively charged, nuclear particles.

For `Z=1`, we have hydrogen, `Z=2`, helium, `Z=3`, lithium.........

But the nuclei can contain different numbers of neutrons, massive, neutrally charged, "nucular" particles. This gives rise to the existence of isotopes. If we look at the simplest element `H`, `Z," the atomic number = "1`, by definition.

Some few hydrogen nuclei contain a neutron to give the `""^2H," deuterium isotope"`; fewer hydrogen nuclei still contain 2 extra neutrons to give the `""^3H," tritium isotope"`. Note that ALL of these isotopes are the element hydrogen, however, each isotope has a different mass.

As atoms get larger, i.e. `Z` increases, the nucleus can generally support greater numbers of isotopes. The atomic mass quoted on the Periodic Table is the weighted average of the individual isotopes.

Capisce?