Ununennium

ununoctium ← ununennium → unbinilium Fr ↑ Uue ↓ Uhe 119Uue Periodic table
Appearance
General properties
Name, symbol, number	ununennium, Uue, 119
Pronunciation	/ˌjuːnəˈnɛniəm/ ew-nə-ne-nee-əm i/uːnuːnˈɛniəm/ oon-oon-e-nee-əm
Element category	alkali metals
Group, period, block	1, 8, s
Standard atomic weight	unknown
Electron configuration	[Uuo] 8s1 (predicted)
Electrons per shell	2, 8, 18, 32, 32, 18, 8, 1 (predicted) (Image)
Physical properties
Atomic properties
Oxidation states	1, 3 (predicted)

Ununennium, also known as eka-francium or element 119, is the temporary name of a hypothetical chemical element in the periodic table that has the temporary symbol Uue and has the atomic number 119. To date, attempted syntheses of this element have been unsuccessful. Since it is below the alkali metals it might have properties similar to those of francium or caesium. Like other alkali metals, it should be extremely reactive with water and air. A predicted oxidation state is +1. Ununennium would be the first element in the eighth period of the periodic table and possibly^{[citation needed]} the seventh alkali metal, though relativistic effects might make it less reactive than francium and caesium.

Unsuccessful attempts at synthesis

The synthesis of ununennium was attempted in 1985 by bombarding a target of einsteinium-254 with calcium-48 ions at the superHILAC accelerator at Berkeley, California. No atoms were identified, leading to a limiting yield of 300 nb.

$\,^{254}_{99}\mathrm{Es} + \,^{48}_{20}\mathrm{Ca} \to \,^{302}_{119}\mathrm{Uue} ^{*} \to \ \ no\ atoms$

It is highly unlikely that this reaction will be useful given the extremely difficult task of making sufficient amounts of ²⁵⁴Es to make a large enough target to increase the sensitivity of the experiment to the required level, due to the rarity of the element, and extreme rarity of the isotope.

Predicted decay characteristics

The alpha-decay half-lives of 1700 nuclei with 100 ≤ Z ≤ 130 have been calculated in a quantum tunneling model with alpha-decay Q-values from different mass estimates. The alpha-decay half-lives predicted for ^291-307119 are of the order of micro-seconds. The highest value of the alpha-decay half-life predicted in the quantum tunneling model with the mass estimates from a macroscopic-microscopic model is ~485 microseconds for the isotope ²⁹⁴119. For ³⁰²119 it is ~163 microseconds.

Target-projectile combinations leading to Z=119 compound nuclei

The below table contains various combinations of targets and projectiles which could be used to form compound nuclei with an atomic number of 119.

Target	Projectile	CN	Attempt result
254Es	48Ca	302Uue	Failure to date

Theoretical calculations on evaporation cross sections

The below table contains various targets-projectile combinations for which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given.

DNS = Di-nuclear system; σ = cross section

Target	Projectile	CN	Channel (product)	σ max	Model	Ref
254Es	48Ca	302Uue	3n (299Uue)	0.5 pb	DNS

See also

• Extended periodic table