Mass spectrometry
Separation: As the ions are moved along a magnetic field, the atoms with a higher mass-to-charge ratio will not be affected as much by the magnetic field, while those with a lower mass-to-charge ratio will be affected more. Most atoms only have a single charge, so with those, the angle of the heavier atoms won't change much, while the angle of the lighter atoms will change a lot. This is because they have more mass compared to their single charge.