The vibration of an atom can be determined in a few ways, including atom interferometry, in which atomic waves are coherently split and later recombined, according to Alex Cronin, an associate professor in the department of physics at the University of Arizona and frequency combs, which use spectrometry to measure vibrations. Pratt’s 2014 article in the Journal of Measurement Science. Good vibrationsĪnother way that the mass of an atom can be found is by measuring its vibration frequency and solving backwards, according to Jon R. That's accurate enough for most purposes. Using a mass spectrometer, physicists have determined the mass of a hydrogen atom to be 1.660538921(73) × 10 -27 kilograms, where the parenthetical digits are not known with complete certainty. That measurement enables physicists to determine the mass of an atom when it has the correct number of electrons, rather than a dearth or surplus of them.

The mass of the electron has also been determined using a mass spectrometer - in that case, electrons were simply sent through the instrument themselves. Lastly, by way of Newton's second law of motion, F=ma, rearranged as m=F/a, the physicists divide the total force acting on the ions by their resulting acceleration to determine the ions' mass. By measuring where and when the stream of ions hits the Faraday cups, the physicists can determine how much they must have accelerated, and in what direction, as a result of the electric and magnetic forces. The ions are then collected by 'Faraday cups' at the end of the tube, generating a current in wires attached to the cups.

Mass of a hydrogen atom