[Chemistry Class Notes] on Charge to Mass Ratio of an Electron Pdf for Exam

Democritus proposed that matter is made up of small units called atoms. Slowly with time, experiments and discoveries scientists proposed that atom is not the ultimate particle. It is made up of three subatomic particles called electron, proton and neutron. Protons and neutrons are found in the nucleus of the atom while electron is found in the shells or orbits around the nucleus. Electrons are negatively charged subatomic particles while proton are positive, and neutron are neutral. Structure of an atom is given below –

Charge on an Electron

Electric charge on an electron is -1.602 10-19C (or experimental value -1.602176634 10-19Coulombs). It is used as a standard unit of charge for subatomic particles. It is called the elementary charge. Symbol of elementary charge is e. The electrical charge on an electron is equal to the charge on proton, but with opposite sign. As the elementary charge is denoted by e, the electron is commonly symbolized by e–. Minus sign denotes negative charge. Charge on an electron is given below in the table in different units. 

 

Mass of an Electron

The intrinsic mass of an electron is approximately 9.109 10-31 kilograms. This mass corresponds to a rest energy of 0.511MeV, according to Einstein’s principle of mass-energy equivalence. We can define its mass in relative terms of proton as well. The mass of an electron is 1/1836 of mass of proton. Mass of electron is given in the table below in different units –

 

As we can see mass of electron is very less so it can be taken as approximately 0amu. 

Charge to Mass Ratio of Electron 

As we have already discussed mass and charge of an electron. So, now its easy to calculate the charge to mass ration of electron. 

Charge of an electron (e) = 1.602*10-19C

Mass of an electron (me) = 9.109 *10-31 kilograms

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If we take value up to six digits after decimal, then it will be 1.758820 1011Ckg-1. 

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