Unbiunium

Unbiunium, ₁₂₁Ubu
Theoretical element
Unbiunium
Pronunciation	/ˌuːnbaɪˈuːniəm/ (OON-by-OON-ee-əm)
Alternative names	eka-actinium, superactinium
Unbiunium in the periodic table
	unbinilium ← unbiunium → unbibium
Atomic number (Z)	121
Group	g-block groups (no number)
Period	period 8 (theoretical, extended table)
Block	g-block
Electron configuration	[Og] 8s2 8p1 (predicted)
Electrons per shell	2, 8, 18, 32, 32, 18, 8, 3; (predicted)
Physical properties
Phase at STP	unknown
Atomic properties
Oxidation states	(+1), (+3) (predicted)
Ionization energies	1st: 429.4 (predicted) kJ/mol ; ;
Other properties
CAS Number	54500-70-8
History
Naming	IUPAC systematic element name
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Unbiunium, also known as eka-actinium or element 121, is a hypothetical chemical element; it has symbol Ubu and atomic number 121. Unbiunium and Ubu are the temporary systematic IUPAC name and symbol respectively, which are used until the element is discovered, confirmed, and a permanent name is decided upon. In the periodic table of the elements, it is expected to be the first of the superactinides, and the third element in the eighth period. It has attracted attention because of some predictions that it may be in the island of stability. It is also likely to be the first of a new g-block of elements.

Unbiunium has not yet been synthesized. It is expected to be one of the last few reachable elements with current technology; the limit could be anywhere between element 120 and 124. It will also likely be far more difficult to synthesize than the elements known so far up to 118, and still more difficult than elements 119 and 120. The teams at RIKEN in Japan and at the JINR in Dubna, Russia have indicated plans to attempt the synthesis of element 121 in the future after they attempt elements 119 and 120.

The position of unbiunium in the periodic table suggests that it would have similar properties to lanthanum and actinium; however, relativistic effects may cause some of its properties to differ from those expected from a straight application of periodic trends. For example, unbiunium is expected to have a s²p valence electron configuration, instead of the s²d of lanthanum and actinium or the s²g expected from the Madelung rule, but this is not predicted to affect its chemistry much. It would on the other hand significantly lower its first ionization energy beyond what would be expected from periodic trends.

^ ^a ^b ^c Hoffman, Darleane C.; Lee, Diana M.; Pershina, Valeria (2006). "Transactinides and the future elements". In Morss; Edelstein, Norman M.; Fuger, Jean (eds.). The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Dordrecht, The Netherlands: Springer Science+Business Media. ISBN 978-1-4020-3555-5.
^ Amador, Davi H. T.; de Oliveira, Heibbe C. B.; Sambrano, Julio R.; Gargano, Ricardo; de Macedo, Luiz Guilherme M. (12 September 2016). "4-Component correlated all-electron study on Eka-actinium Fluoride (E121F) including Gaunt interaction: Accurate analytical form, bonding and influence on rovibrational spectra". Chemical Physics Letters. 662: 169–175. Bibcode:2016CPL...662..169A. doi:10.1016/j.cplett.2016.09.025. hdl:11449/168956.

[Haire-1] Hoffman, Darleane C.; Lee, Diana M.; Pershina, Valeria (2006). "Transactinides and the future elements". In Morss; Edelstein, Norman M.; Fuger, Jean (eds.). The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Dordrecht, The Netherlands: Springer Science+Business Media. ISBN 978-1-4020-3555-5.

[Amador-2] Amador, Davi H. T.; de Oliveira, Heibbe C. B.; Sambrano, Julio R.; Gargano, Ricardo; de Macedo, Luiz Guilherme M. (12 September 2016). "4-Component correlated all-electron study on Eka-actinium Fluoride (E121F) including Gaunt interaction: Accurate analytical form, bonding and influence on rovibrational spectra". Chemical Physics Letters. 662: 169–175. Bibcode:2016CPL...662..169A. doi:10.1016/j.cplett.2016.09.025. hdl:11449/168956.

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