The Positronium atom is made up of no neutons and no protons. It consists of 1 electron and 1 positron(antielectron) orbiting around a common center of gravity. The Chemistry of Positronium is analogous to that of H. radical. It undergoes addition reactions with alkenes/alkynes, it can reduce Iron(III) to Iron(II), it can undergoe substitution with Cl2 to make PsCl and Cl..
Positronium would be above Hydrogen in the periodic table.