<P> 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 its mass - to - charge ratio was much smaller than that of the hydrogen ion H. In 1898 , Wilhelm Wien separated ions ( canal rays ) according to their mass - to - charge ratio with an ion optical device with superimposed electric and magnetic fields ( Wien filter ) . In 1901 Walter Kaufman measured the increase of electromagnetic mass of fast electrons ( Kaufmann -- Bucherer -- Neumann experiments ) , or relativistic mass increase in modern terms . In 1913 , Thomson measured the mass - to - charge ratio of ions with an instrument he called a parabola spectrograph . Today , an instrument that measures the mass - to - charge ratio of charged particles is called a mass spectrometer . </P>
<P> 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 its mass - to - charge ratio was much smaller than that of the hydrogen ion H. In 1898 , Wilhelm Wien separated ions ( canal rays ) according to their mass - to - charge ratio with an ion optical device with superimposed electric and magnetic fields ( Wien filter ) . In 1901 Walter Kaufman measured the increase of electromagnetic mass of fast electrons ( Kaufmann -- Bucherer -- Neumann experiments ) , or relativistic mass increase in modern terms . In 1913 , Thomson measured the mass - to - charge ratio of ions with an instrument he called a parabola spectrograph . Today , an instrument that measures the mass - to - charge ratio of charged particles is called a mass spectrometer . </P>
who determined the mass to charge ratio of an electron
who determined the mass to charge ratio of an electron
J.J. Thomson
J.J. Thomson