Neutronium
hypothetical substance composed only of neutrons
Neutronium (or element zero) is a hypothetical element built solely from neutrons. The word was coined by scientist Andreas von Antropoff in 1926 for the hypothetical "element of atomic number zero" (with no protons in its nucleus) that he placed at the head of the periodic table (denoted by -).
History
Ernest Rutherford proposed a hypothetical neutral particle in 1920, as combination of a proton and an electron with the atomic nucleus. The proposed particle would be discovered by James Chadwick in 1932, but the composition of this particle would ultimately found not to correspond to an electron plus a proton. In the intervening years the particle came to be called a neutron. a term invented in a 1926 paper by Andreas von Antropoff which also introduced the term neutronium. The work by von Antropoff was on a new proposed form of the periodic table and included a conjectured element made up of neutrons with no protons or electrons, which he placed as the chemical element of atomic number zero at the head of his new version of the periodic table. This neutronium 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). All of these authors believed neutronium would be a noble gas.
Chemistry
Neutronium is considered by some chemists to be a legitimate element with atoms called neutrons, an element with no chemical properties whatsoever.
Begin with the source’s own compact description: “Neutronium” is hypothetical substance composed only of neutrons. The dossier treats that line as a proposition to test through Neutronium, hypothetical and substance, not as a finished interpretation.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Sep 21, 2026. The linked authority identifier is Q1195471. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1926, 1920, 1932 and 1928.
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This entry incorporates text from “Neutronium” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.