Question

how can we prove that electron is a fundamental particle ?

Answer 1

Electrons are considered fundamental because there’s a lot of experimental evidence that suggests they are. In the standard model, they’re fundamental particles, and no experiment ever conducted on earth has indicated otherwise. There’s no a priori reason that they have to be fundamental, however — perhaps at obscenely high energies something more interesting happens.

In the standard model, the most accurate model of nature ever made by man, electrons are fundamental, and everything we observe about them agrees with that fact.

Hope that helps!

Answer 2

Atom is composed of neutron, proton and electron. After the discovery of neutron proton and electron it was observed that electron is the smallest of all the particles. So it was accepted the fundamental particle of all matter.