http://us.wow.com/wiki/Protonium?s_chn=5&s_pt=aolsem&type=content&v_t=content Protonium (symbol: Pn), also known as antiprotonic hydrogen, is a type of exotic atom in which a proton (symbol: p) and an antiproton (symbol: p) orbit each other.[1] Since protonium is a bound system of a particle and its corresponding antiparticle,