Unsepttrium

Unsepttrium is the temporary systematic name for hypothetical element 173, an element beyond the currently confirmed periodic table. Its existence and chemical properties have not been established.

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IUPAC systematic element names: Provisional element names formed from numerical roots corresponding to an element’s atomic number. Unsepttrium combines roots for the digits in atomic number 173.
Island of stability: A predicted region of comparatively long-lived superheavy nuclei associated with particular proton and neutron numbers. It motivates searches for superheavy nuclei but does not establish element 173’s stability.
Superheavy element: A chemical element with a very high atomic number, typically produced through nuclear reactions. Element 173 would lie far beyond the superheavy elements synthesized so far.
IUPAC: The International Union of Pure and Applied Chemistry, which develops standards for chemical nomenclature and terminology. IUPAC established the systematic naming rules that generate unsepttrium.
Atomic number: The number of protons in an atom’s nucleus, which defines its chemical element. The number 173 specifies which hypothetical element the name denotes.
Nuclear shell model: A model describing protons and neutrons as occupying discrete energy levels in atomic nuclei. Its shell effects inform estimates of whether nuclei with 173 protons could persist.
Nuclear fusion: A process in which atomic nuclei combine to form a heavier nucleus. Creating element 173 would require a nuclear reaction capable of assembling its nucleus.
Dmitri Mendeleev: A Russian chemist who developed a periodic table and predicted properties of undiscovered elements. His predictions helped establish the idea that the periodic table could extend beyond known elements.
Periodic table: A tabular arrangement of chemical elements ordered by atomic number and recurring chemical properties. Element 173 would extend the table beyond all confirmed elements.
Nuclear drip line: The boundary beyond which a nucleus cannot bind another proton or neutron. It constrains which neutron counts could accompany 173 protons in a bound nucleus.