Answer: The three sub-atomic particles are the following: protons, electrons and neutrons.
Explanation: Protons are positively charged particles and are found in the nucleus of an atom. This positively charged particles were associated to Ernest Rutherford with regards to its discovery. Along with the protons in the nucleus there were also neutrons that are neutral in charge. The third subatomic particles were the electrons. They were negatively charged particles and are found in the electron cloud region outside the nucleus. There are specific number of Electrons arrange in each orbitals, since they are prone to be moved in cases of chemical reactions. It was discovered by JJ Thompson using cathode rays and coined its name. For an atom to be electrically neutral or stable the number of electrons and protons must be equal.