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— ← neutronium → hydrogen

—
↑
Nt [not official]
↓
—

0Nt

Periodic table

Appearance

General properties

Name, symbol, number

neutronium, Nt [not official], 0

Element category

—

Group, period, block

—, —, —

Standard atomic weight

(1) g·mol⁻¹

Electron configuration

0s⁰

Electrons per shell

0 (Image)

Physical properties

Atomic properties

Oxidation states

Electronegativity

0.00 (Pauling scale) (Pauling scale)

Most stable isotopes

Main article: Isotopes of neutronium

iso	NA	half-life	DM	DE (MeV)	DP
¹Nt	?	885.7±0.8 s	β⁻	1.294	¹H

Neutronium is a proposed name for a substance composed purely out of neutrons. The term was originally used in science fiction and in popular literature to refer to a highly dense phase of matter composed primarily of neutrons. The word was coined by scientist Andreas von Antropoff in 1926 (before the discovery of the neutron itself) for the conjectured 'element of atomic number zero' that he placed at the head of the periodic table.^[1]^[2] However, the meaning of the term has changed over time, and from the last half of the 20th century onward it has been used legitimately to refer to extremely dense phases of matter resembling the neutron-degenerate matter postulated to exist in the cores of neutron stars.

1 Neutronium and neutron stars
2 Neutronium and the periodic table
3 Neutronium in fiction
4 See also
5 References
6 Bibliography

Neutronium and neutron stars

Main article: Neutron star

The term neutronium is used in popular 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). This term is very rarely used in scientific literature, for two reasons:

There is no universally agreed-upon definition for the term "neutronium".
There is considerable uncertainty over the composition of the material in the cores of neutron stars (it could be neutron-degenerate matter, strange matter, quark matter, or a variant or combination of the above).

When neutron star core material is presumed to consist mostly of free neutrons, it is typically referred to as neutron-degenerate matter in scientific literature.

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 as a noble gas in the middle of several spiral representations of the periodic system for classifying the chemical elements, such as the 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.^[3] 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, is not a bound particle, but has been proposed as an extremely short-lived state produced by nuclear reactions involving tritium.
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.^[4]^[5]
Pentaneutron: Calculations indicate that the hypothetical pentaneutron state, consisting of a cluster of five neutrons, would not be bound.
And so on, through the numbers, up to icosaneutron, with 20 neutrons.^[6]

If one accepts neutronium to be an element, the above mentioned neutron clusters would be the isotopes of that element, if their existence can be confirmed.

Neutronium in fiction

The term neutronium has been popular in science fiction since at least the middle of the 20th century. It typically refers to an extremely dense, incredibly strong form of matter. While presumably inspired by the concept of neutron-degenerate matter in the cores of neutron stars, the material used in fiction bears at most only a superficial resemblance, usually depicted as an extremely strong solid under Earth-like conditions, or possessing exotic properties such as the ability to manipulate time and space. In contrast, all proposed forms of neutron star core material are fluids and are extremely unstable at pressures lower than that found in stellar cores.

Noteworthy appearances of neutronium in fiction include the following:

In Hal Clement's short story Proof (1942), neutronium is the only form of solid matter known to Solarians, the inhabitants of the Sun's interior.
In Vladimir Savchenko's Black Stars (1960), neutronium is mechanically and thermally indestructible substance. It is also used to make antimatter, which leads to a fusion explosion accident.
In Doctor Who (1963), neutronium is a substance which can shield spaces from time-shear when used as shielding in time-vessels.
In Larry Niven's Known Space fictional universe (1964), neutronium is actual neutron star core material. Niven does not make assumptions about its strength, but imagines that small blobs of it could be artificially created under pressure, and their instability overcome by containing them in slaver stasis feilds.
In the Star Trek universe, neutronium is an extremely hard and durable substance, often used as armor, which conventional weapons cannot penetrate or even dent.
In the Star Wars expanded universe, neutronium is a metal used to make the durasteel alloy.^{[citation needed]}
In the computer games Master of Orion (1993), Master of Orion 2 (1996), Master of Orion 3 (2003), and Sid Meier's Alpha Centauri (1999), neutronium is one of the strongest armor types. MoO1 - strongest; MoO2 & SMAC - 3rd strongest. MoO1 and MoO2 also feature "neutronium bombs", which are extremely powerful planetary bombardment weapons which causes damage due to gravitic effects.
In Peter F. Hamilton's novel The Neutronium Alchemist (1997), neutronium is created by the "aggressive" setting of a superweapon.
In Stargate SG-1 (1997), neutronium is a substance which is the basis of the technology of the advanced Asgard race, as well as a primary component of human-form Replicators; and apparently occures naturally as a mineral in the crusts on some earthlike planets.