Question

what is electron ? Explain it

Answer 1

1)electron is the negatively charged particle in an atom
2)it revolves around the nucleus
3)its mass is negligible when we consider atomic mass 

Answer 2

an electron is a part of an atom. It revolves in the outer shells of the atom and is negatively charged. An atom can either gain electrons  to become negatively charged or it can lose electrons to become positively charged.