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

1 Answer
anor277
Aug 27, 2016

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?

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