Neutronium (or neutrium, neutrite, or element zero) is a hypothetical substance made purely of

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

s. The word was coined by scientist Andreas von Antropoff in 1926 (before the 1932

discovery of the neutron The discovery of the neutron and its properties was central to the extraordinary developments in atomic physics in the first half of the 20th century. Early in the century, Ernest Rutherford developed a crude Rutherford model, model of the atom, ...

) for the hypothetical "element of atomic number zero" (with no protons in its nucleus) that he placed at the head of the

periodic table The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows (" periods") and columns (" groups"). It is an icon of chemistry and is widely used in physics and other s ...

(denoted by -). However, the meaning of the term has changed over time, and from the last half of the 20th century onward it has been also used to refer to extremely dense substances resembling the neutron-degenerate matter theorized to exist in the cores of

neutron star A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses ...

In neutron stars

Neutronium is used in popular physics literature to refer to the material present in the cores of neutron stars (stars which are too massive to be supported by electron degeneracy pressure and which collapse into a denser phase of matter). In scientific literature the term "neutron-degenerate matter" or simply neutron matter is used for this material.

Hypothetical multi-neutrons

The term "neutronium" was coined in 1926 by Andreas von Antropoff for a conjectured form of matter made up of neutrons with no

proton A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...

s or

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

s, which he placed as the

chemical element A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its ...

atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of protons and neutrons, this is equal to the proton number (''n''p) or the number of pro ...

zero at the head of his new version of the

. 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), Edgar Emerson (1944), and John D. Clark (1950). The term is not used in the scientific literature either for a condensed form of matter, or as an element, and theoretical analysis expects no bound forms of neutrons without protons.

Scattering resonances with multiple neutrons

The dineutron, containing two neutrons, is not a stable bound particle, but an extremely short-lived resonance state produced by nuclear reactions in the decay of beryllium-16. Evidence reported in 2012 for the resonance was disputed, but new work reportedly clears up the issues. The dineutron hypothesis had been used in theoretical studies of the structure of exotic nuclei. For example ¹¹Li is modeled as a dineutron bound to a ⁹Li core. 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 Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons (protons and neutrons) and nuclei. According to current theories, the first nuclei were formed a few minutes after the Big Bang, through nuclear reactions in ...

and the

abundance of the chemical elements The abundance of the chemical elements is a measure of the Type–token distinction#Occurrences, occurrences of the chemical elements relative to all other elements in a given environment. Abundance is measured in one of three ways: by mass fractio ...

. A trineutron state consisting of three bound neutrons has not been detected, and is not expected to be bound. A tetraneutron is a hypothetical particle consisting of four bound neutrons. Reports of its existence have not been replicated. Calculations indicate that the hypothetical pentaneutron state, consisting of a cluster of five neutrons, would not be bound.

References

{{Portal bar, Physics, Chemistry, Astronomy, Stars, Science Concepts in astrophysics Exotic matter Neutron Fictional materials

In neutron stars

Hypothetical multi-neutrons

Scattering resonances with multiple neutrons

See also

References