Question

List the three atomic particles, their relative masses and their, charges. why is the mass of an electron ignored when calculating the mass of an atom?

Answer 1

The three atomic particles are neutrons, protons and electrons.

Neutrons and protons are both located in the nucleus of an atom.
Neutrons mass is about 1.
Protons are the same.

Electrons are located outside of the nucleus. They float around, and their mass is 0. They're ignored when calculating the mass of an atom because most of the atoms weight is in the nucleus! :)