Mass-to-charge ratio refers to the molecular or atomic mass number and "z" to the charge number of the ion; however, the quantity of "m"/"z" is dimensionless by definition. An ion of 100 atomic mass units ("m" = 100) carrying two charges ("z" = 2) will be observed at "m"/"z" = 50. In the 19th century, the mass-to-charge ratios of some ions were measured by electrochemical methods. In 1897, the mass-to-charge ratio of the electron was first measured by J. J. Thomson. By doing this, he showed that the electron was in fact a particle with a mass and a charge, and that
Mass-to-charge ratio the mass of a particle. Often, the charge-to-mass ratio can be determined from observing the deflection of a charged particle in an external magnetic field. The cyclotron equation, combined with other information such as the kinetic energy of the particle, will give the charge-to-mass ratio. One application of this principle is the mass spectrometer. The same principle can be used to extract information in experiments involving the cloud chamber. The ratio of electrostatic to gravitational forces between two particles will be proportional to the product of their charge-to-mass ratios. It turns out that gravitational forces are negligible on the subatomic