ununhexium ← Ununseptium → ununoctium At ↑ Uus ↓ (Uhs) 117Uus Periodic table
Appearance
Unknown
General properties
Name, symbol, number	Ununseptium, Uus, 117
Category notes	Unknown
Group, period, block	17, 7, p
Standard atomic weight	Unknown g·mol−1
Electron configuration	Unknown
Electrons per shell	2,8,18,32,32,18,7 (predicted) (Image)
Physical properties
Atomic properties
Miscellanea
CAS registry number	87658-56-8
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Ununseptium (pronounced /uːnuːnˈsɛptiəm/ ( listen)^[1] oon-oon-SEP-tee-əm) is the temporary name of an undiscovered chemical element with the temporary symbol Uus and atomic number 117. It is the only missing element in period 7 of the periodic table. Since it is placed below the halogens it may share qualities similar to astatine or iodine. The first attempt to synthesize this element is currently underway at the Flerov Laboratory of Nuclear Reactions in Dubna, Russia.

Contents 1 History 1.1 Naming 1.2 Current experiments 1.3 Future experiments 2 Isotopes and nuclear properties 2.1 Nucleosynthesis 2.1.1 Target-projectile combinations leading to Z=117 compound nuclei 2.2 Theoretical calculations 2.2.1 Evaporation residue cross sections 2.2.2 Decay characteristics 3 Chemical properties 3.1 Predicted chemical properties 4 References

[edit] History

[edit] Naming

The element with Z=117 is historically known as eka-astatine (see 'eka' terminology). The name ununseptium is a systematic element name, used as a placeholder until the element is discovered, the discovery is acknowledged by the IUPAC, and the IUPAC decides on a name. Usually, the name suggested by the discoverer(s) is chosen.

According to current guidelines from IUPAC, the ultimate name for all new elements should end in "-ium", which means the name for element 117 may end in -ium, not -ine, even if ununseptium turns out to be a halogen.^[2]

[edit] Current experiments

The team at the Flerov laboratory of nuclear reactions has begun an experiment to synthesize element 117 using the reaction^[3][4]

4820Ca + 24997Bk → 297117Uus^* → 294117Uus + 310n.

The expected cross-section is of the order of ~2 pb. The expected evaporation residues, ²⁹³117 and ²⁹⁴117, are predicted to decay via relatively long decay chains as far as isotopes of dubnium or lawrencium.

Calculated decay chains from the parent nuclei 293Uus and 294 Uus[5]

Calculated excitation function for the production of the compound nucleus 297117 from the reaction 249Bk( 48Ca,xn) [5]

[edit] Future experiments

The team at the GSI in Darmstadt, recently acknowledged as the discoverers of element 112 (see ununbium) have begun experiments aiming towards a synthesis of element 117. The GSI have indicated that if they are unable to acquire any ²⁴⁹Bk from the United States, which is likely given the situation regarding the attempt in Russia, they will study the reaction ²⁴⁴Pu(⁵¹V,xn) instead, or possibly ²⁴³Am(⁵⁰Ti,xn).^[6]

[edit] Isotopes and nuclear properties

[edit] Nucleosynthesis

[edit] Target-projectile combinations leading to Z=117 compound nuclei

The below table contains various combinations of targets and projectiles which could be used to form compound nuclei with Z=117.

Target	Projectile	CN	Attempt result
208Pb	81Br	289117	Reaction yet to be attempted
232Th	59Co	291117	Reaction yet to be attempted
238U	55Mn	293117	Reaction yet to be attempted
237Np	54Cr	291117	Reaction yet to be attempted
244Pu	51V	295117	Reaction yet to be attempted
243Am	50Ti	293117	Reaction yet to be attempted
248Cm	45Sc	293117	Reaction yet to be attempted
249Bk	48Ca	297117	In progress
249Cf	41K	290117	Reaction yet to be attempted

[edit] Theoretical calculations

[edit] Evaporation residue 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)	σmax	Model	Ref
209Bi	82Se	291117	1n (290117)	15 fb	DNS	[7]
209Bi	79Se	288117	1n (287117)	0.2 pb	DNS	[7]
232Th	59Co	291117	2n (289117)	0.1 pb	DNS	[7]
238U	55Mn	293117	2-3n (291,290117)	70 fb	DNS	[7]
244Pu	51V	295117	3n (292117)	0.6 pb	DNS	[7]
248Cm	45Sc	293117	4n (289117)	2.9 pb	DNS	[7]
246Cm	45Sc	291117	4n (287117)	1 pb	DNS	[7]
249Bk	48Ca	297117	3n (294117)	2.1 pb ; 3 pb	DNS	[7][8]
247Bk	48Ca	295117	3n (292117)	0.8, 0.9 pb	DNS	[8][7]

[edit] Decay characteristics

Theoretical calculations in a quantum tunneling model with mass estimates from a macroscopic-microscopic model predict the alpha-decay half-lives of isotopes of the element 117 (namely, ^289-303117) to be around 0.1–40 ms.^[9][10][11]

[edit] Chemical properties

[edit] Predicted chemical properties

Certain chemical properties, such as bond lengths, are predicted to differ from what one would expect based on periodic trends from the lighter halogens (because of relativistic effects).^[12]

[edit] References

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