Unsepttrium

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Unsepttrium, ₀₀Ust

Unsepttrium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Uue ↑ Ust ↓ (Bbs) unseptbium ← unsepttrium → unseptquadium
Electrons per shell	2, 8, 18, 32, 50, 33, 18, 8, 4 (predicted)
Atomic properties
Oxidation states	Template:Infobox element/symbol-to-oxidation-state: Symbol "Ust" not known
Isotopes of unsepttrium v e
Template:infobox unsepttrium isotopes does not exist
Category: Unsepttrium view talk edit | references

Unsepttrium (/ˌuːnsɛptriəm/), also called dvi-francium^[source?] , eka-Ununennium, or element 173, is a possible chemical element which has never been seen in nature, and it has never been made. It is not known if this element is possible, as the instabilities may show that the periodic table ends soon after the island of stability at unbihexium;^[1] but it is likely the heaviest possible neutral element. Its atomic number is 173 and its atomic symbol is Ust.

The name unsepttrium is a temporary IUPAC systematic element name.

Although Richard Feynman said^[2] that a simple interpretation of the relativistic Dirac equation runs into problems with electron orbitals at Z > 1/α = 137, that probably means that neutral atoms cannot exist beyond untriseptium, and that a periodic table of elements based on electron orbitals stops at this point, a deeper analysis shows the limit to be to be Z ≈ 173, meaning that neutral atoms most likely cannot exist with an atomic number greater than 173.^[3] This makes unsepttrium theoretically the heaviest neutral element possible.

• untriseptium