How do you think sub-atomic particles (protons, neutrons, and electrons) affect the atom and its behavior?

Protons and Neutrons affect the mass. Protons and Electrons change the charge of the atom (positively or negatively charged). Valence electrons are the ones that do fun stuff in chemical reactions, they are responsible for making/breaking bonds, at least to my understanding.

Hope this helps.

Except hold on to his or her beliefs even if there is no evidence for those beliefs.