Skip to main content

The National MagLab is funded by the National Science Foundation and the State of Florida.

Mass Spectra

Mass spectrum reveals how many isotopes of a given element are to be found in a material.

Isotopes are atoms of the same element that have different atomic weights, due to varying numbers of neutrons (the neutrally-charged particles found in an atom's nucleus).

Mass spectrometers measure the range of possible masses of those isotopes. Depending on the isotopes that make up a particular sample, researchers glean clues about its origin and how it was formed.

The number of isotopes of a given element found in a material is known as the isotope’s relative abundance – relative, that is, to the other isotopes found in the sample.


  1. Use the drop-down menu to select from seven different elements.
  2. Observe the mass spectrum for that element.
  3. As you can see, gallium, for example, has two different isotopes. One of them – the one with an atomic weight of 69 – is more abundant than the other.