Question

What function do Protons, Neutrons, and Electrons have in an atom?

Answer 1

The proton in the positively-charged particle and the number of protons give the atom's element name. Each element has a different amount of protons.
Neutrons are responsible for combining with protons in the nucleus together to be held by the strong force. Too many neutrons in an atom will result in radioactive decay due to the neutrons' force overpowering the strong force.

Electrons are the weirdest particles. They are the smallest ones, and have a mass of
$\frac{1}{1836}$ of a proton or a neutron. They are negatively-charged, and the valence electrons are responsible for the reactivity of an atom.