Atomic and nuclear properties of positronium (Ps):
Positronium (Z = 1 atom with e+ as nucleus)
* Ground state binding energy = Ry/2.
| Atomic number
1.097 526 752 (5)
1.021 991 03 (9)
| Mean lifetime|
Singlet (p-Ps): 125
Triplet (o-Ps): 142.05 ± 0.02 |
Is it reasonable to consider Ps as a chemical element?
It is bound electronically. If we consider atoms as having orbital
then the positron plays the role of nucleus.
It has a rich chemistry, as Google searches on "positronium halides,"
"positronium compounds," and other strings show. There are international
conferences on positronium chemistry.
In other exotic atoms such as muonium, pionium, and kaonium, the bound
muon or meson plays the role of an orbital electron instead of being the
nucleus. Although e−π+ and other such
atoms might equally well be
regarded as elements, as would atoms with
hypernuclei, these contain
An isolated positron is presumably as stable as an electron.
One serious objection is that the positronium "nucleus" has non-zero
(e−π+ and atoms with hypernuclei have nuclei with lepton number
zero, as do "normal" nuclei.)
- We are physicists, not chemists.