There are three atomic particles within an atom. The first is an electron that orbits the nucleus, has a very small mass (1/2000 amu) and has a negative charge. Next is the neutron that is in the nucleus, has a large mass (1 amu) and has a neutral charge. Last is a proton which is also in the nucleus, has a mass of 1 amu, and has a positive charge. So a proton would be the subatomic particle you are looking for. :)