Ununennium

Ununennium, or element 119, is a predicted chemical element. Its symbol is Uue. Ununennium and Uue are substitute names made by the IUPAC, (meaning "one-one-nine-ium" in Latin) until permanent names are made. Ununennium is the element with the smallest atomic number that has not been created yet. Qualities of Ununennium are unknown, but many are predicted. It is predicted all isotopes will be radioactive. It is thought to be an alkali metal.^[8]

Ununennium, ₀₀Uue

Ununennium
Pronunciation	/ˌuːn.uːnˈɛniəm/ (listen) ​(OON-oon-EN-ee-əm)
Alternative names	element 119, eka-francium
Ununennium 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 Fr ↑ Uue ↓ (Ust) oganesson ← ununennium → unbinilium
Group	group 1: hydrogen and alkali metals
Period	period 8 (theoretical, extended table)
Block	s-block
Electron configuration	[Og] 8s1 (predicted)[1]
Electrons per shell	2, 8, 18, 32, 32, 18, 8, 1 (predicted)
Physical properties
Phase at STP	unknown (could be solid or liquid)[1]
Melting point	273–303 K ​(0–30 °C, ​32–86 °F) (predicted)[1]
Boiling point	903 K ​(630 °C, ​1166 °F) (predicted)[2]
Density (near r.t.)	3 g/cm3 (predicted)[1]
Heat of fusion	2.01–2.05 kJ/mol (extrapolated)[3]
Atomic properties
Oxidation states	(+1), (+3), (+5) (predicted)[1][4]
Electronegativity	Pauling scale: 0.86 (predicted)[5]
Ionization energies	1st: 463.1 kJ/mol 2nd: 1698.1 kJ/mol (predicted)[6]
Atomic radius	empirical: 240 pm (predicted)[1]
Covalent radius	263–281 pm (extrapolated)[3]
Other properties
Crystal structure	​body-centered cubic (bcc) (extrapolated)[7]
CAS Number	54846-86-5
History
Naming	IUPAC systematic element name
Isotopes of ununennium v e
Template:infobox ununennium isotopes does not exist
Category: Ununennium view talk edit | references

Many attempts have been made by American, German, and Russian teams to make ununennium but all have failed. Japanese and Russian teams failed to produce the element after work in both 2019 and 2020. The work of of the Japanese team is ongoing, although no atoms of ununennium have ever been observed.

Predicted chemistry

Ununennium's spot on the periodic table is a sign that it may be similar to lighter elements such as lithium, sodium, potassium, rubidium, caesium, and francium; however, some of its properties may be different from what is expected. For example, ununennium might be less reactive than caesium and francium and will behave more like potassium or rubidium.

Uses

As of 2025, it has not been made and has no use.