Neutronium - Neutronium and The Periodic Table

Neutronium and The Periodic Table

The term "neutronium" was coined in 1926 by Professor Andreas von Antropoff for a conjectured form of matter made up of neutrons with no protons, which he placed as the chemical element of atomic number zero at the head of his new version of the periodic table. It was subsequently placed in the middle of several spiral representations of the periodic system for classifying the chemical elements, such as those of Charles Janet (1928), E. I. Emerson (1944), John D. Clark (1950) and in Philip Stewart's Chemical Galaxy (2005).

Although the term is not used in the scientific literature either for a condensed form of matter, or as an element, there have been reports that, besides the free neutron, there may exist two bound forms of neutrons without protons. If neutronium were considered to be an element, then these neutron clusters could be considered to be the isotopes of that element. However, these reports have not been further substantiated. Further information can be found in the following articles:

• Mononeutron: Isolated neutrons undergo beta decay with a mean lifetime of approximately 15 minutes (half-life of approximately 10 minutes), becoming protons (the nucleus of hydrogen), electrons and antineutrinos.
• Dineutron: The dineutron, containing two neutrons was unambiguously observed in the decay of beryllium-16, in 2012 by researchers at Michigan State University. It is not a bound particle, but had been proposed as an extremely short-lived state produced by nuclear reactions involving tritium. It has been suggested to have a transitory existence in nuclear reactions produced by helions that result in the formation of a proton and a nucleus having the same atomic number as the target nucleus but a mass number two units greater. There had been evidence of dineutron emission from neutron-rich isotopes such as beryllium-16 where mononeutron decay would result in a less stable isotope. The dineutron hypothesis had been used in nuclear reactions with exotic nuclei for a long time. Several applications of the dineutron in nuclear reactions can be found in review papers. Its existence has been proven to be relevant for nuclear structure of exotic nuclei. A system made up of only two neutrons is not bound, though the attraction between them is very nearly enough to make them so. This has some consequences on nucleosynthesis and the abundance of the chemical elements.
• Trineutron: A trineutron state consisting of three bound neutrons has not been detected, and is not expected to exist even for a short time.
• Tetraneutron: A tetraneutron is a hypothetical particle consisting of four bound neutrons. Reports of its existence have not been replicated. If confirmed, it would require revision of current nuclear models.
• Pentaneutron: Calculations indicate that the hypothetical pentaneutron state, consisting of a cluster of five neutrons, would not be bound.
• And so on.

Although not called "neutronium", the National Nuclear Data Center's Nuclear Wallet Cards lists as its first "isotope" an "element" with the symbol n and atomic number Z = 0 and mass number A = 1. This isotope is described as decaying to element H with a half life of 10.24±0.02 minutes.