What is Positronium?
[[File:Positronium.svg|thumb|An example of a Positronium atom, with a positron and an electron in the same orbital]] '''Positronium''' is an onium, a type of [[exotic atom]] that is made of a particle and its antiparticle. In Positronium, one [[positron]] and one [[electron]] are bonded together. The positron replaces a proton that would normally be present in a [[Hydrogen]] [[atom]]. They both stay in the same [[Atomic orbital|orbital]]. The atom is unstable, and a few nanoseconds after it is created, the positron and the electron collide, destroying the Positronium and forming two [[gamma rays]]. == Positronium molecules == Positronium can form molecules, like normal atoms. It can bond with both other exotic atoms and normal atoms. === Di-positronium === Di-positronium is a simple molecule made from two positronium atoms bonded together. It was predicted in 1946 by John Archibald Wheeler, but was discovered in 2007 by David Cassidy and Allen Mills, when they fired [[positron]]<nowiki/>s at molecules of [[silicon dioxide]]. === Positronium hydride === Positronium hydride, also called hydrogen positride, is an [[Exotic atom|exotic molecule]] made of an atom of [[hydrogen]] bonded to a positronium atom. It was predicted in 1951 by A Ore, but was not discovered until 1990 by R. Pareja and R. Gonzalez, who discovered it when they trapped positronium in hydrogen-[[magnesia]] crystals. [[Category:Physics]]