Ununseptium Element Facts


Six atoms of ununseptium may have been detected. Image Courtesy: Oak Ridge National Laboratory


Data Zone

Classification: Ununseptium is a halogen (presumed)
Atomic weight: (294), no stable isotopes
State: solid (presumed)
Melting point:
Boiling point:
Electrons: 117
Protons: 117
Neutrons in most abundant isotope: 177
Electron shells: 2, 8, 18, 32, 32, 18, 7
Electron configuration: [Rn] 5f14 6d10 7s2 7p5 (presumed)
Show more, including: Heats, Energies, Oxidation, Reactions, Compounds, Radii, Conductivities
Specific heat capacity
Heat of fusion
Heat of atomization
Heat of vaporization
1st ionization energy
2nd ionization energy
3rd ionization energy
Electron affinity
Minimum oxidation number
Min. common oxidation no.
Maximum oxidation number
Max. common oxidation no.
Electronegativity (Pauling Scale)
Polarizability volume
Reaction with air
Reaction with 15 M HNO3
Reaction with 6 M HCl
Reaction with 6 M NaOH
Atomic radius
Ionic radius (1+ ion)
Ionic radius (2+ ion)
Ionic radius (3+ ion)
Ionic radius (1- ion)
Ionic radius (2- ion)
Ionic radius (3- ion)
Thermal conductivity
Electrical conductivity
Freezing/Melting point:

An animation showing how ununseptium was synthesized. From Kwei-Yu Chu of the Lawrence Livermore National Laboratory.

The cyclotron at Dubna

The heavy ion cyclotron U-400 in Dubna, where ununseptium may have been synthesized.

A combination of experiments and computer simulations enable predictions to be made of deformations and shapes of the heaviest elements in and beyond the current periodic table.

A combination of experiments and computer simulations enable predictions to be made of deformations and shapes of the heaviest elements in and beyond the current periodic table. Photo: ORNL

Discovery of Ununseptium

Dr. Doug Stewart

In 2009, the first atoms of element 117 were made in the Flerov Laboratory of Nuclear Reactions in Dubna, Russia. Evidence of the synthesis was published in April 2010, by scientific teams from Russia and the United States of America. (1), (2)

The research effort, led by Yuri Oganessian, was a collaboration between the Joint Institute of Nuclear Research (Dubna, Russia); the Research Institute for Advanced Reactors, Dimitrovgrad; Lawrence Livermore National Laboratory; Oak Ridge National Laboratory; Vanderbilt University, Tennessee; and the University of Nevada, Las Vegas.

The discovery has not yet been verified by IUPAC. Ununseptium’s place in the periodic table is unofficial until IUPAC validates its existence.

Ununseptium was made by a fusion reaction of element 20 with element 97: calcium-48 with berkelium-249.

Calcium ions were formed into a beam in a cyclotron (a particle accelerator) and fired at a target layer of berkelium deposited 300 nm thick on titanium foil.

The first bombardment lasted 70 days. The berkelium was bombarded with over 7 trillion calcium-48 ions per second, accelerated to about 10% of the speed of light.

The data suggest five nuclei of interest were produced during the 70 day bombardment. As a consequence of the high energy of the impacts that created them, these nuclei instantly lost thermal energy by emitting four neutrons to form ununseptium-293.

The ununseptium-293 (approximate half-life 14 ms) decayed by alpha emission into element 115 (ununpentium). (2), (3)

In a second bombardment lasting 50 days, the speed of the bombarding calcium-48 ions was reduced. The resulting impacts were of lower energy and the single nucleus of interest that formed needed to emit just three neutrons to lose its excess energy, leading to the heavier ununseptium-294 isotope. The data suggest one atom of ununseptium-294 (approximate half-life 78 ms) was formed in the bombardment, decaying again to element 115.

As a result of its position in Group 17 of the periodic table, ununseptium is expected to have chemical properties characteristic of the halogens. The effects of relativistic electrons, however, may result in partial metalloid properties.

Too little of the element has been synthesized for its chemical properties to be confirmed.

Jim Roberto from Oak Ridge said: “New isotopes observed in these experiments continue a trend toward higher lifetimes for increased neutron numbers, providing evidence for the proposed ‘island of stability’ for super-heavy nuclei.”

The joint teams at JINR in Dubna and Lawrence Livermore in California have published evidence for the synthesis of elements 113, 114, 115, 116, 117 and 118.

IUPAC has accepted the discoveries of element 114 (flerovium/ununquadium) and element 116 (livermorium/ununhexium). It has not yet considered the evidence for the discovery of element 117 (ununseptium).

IUPAC requires stronger evidence before it will confirm the synthesis of element 113 (ununtrium), element 115 (ununpentium), or element 118 (ununoctium).

UPDATE: The discovery of elements 113, 115, 117 and 118 was formally accepted on December 30, 2015 by IUPAC and IUPAP, completing the seventh row of the periodic table.

Appearance and Characteristics

Harmful effects:

Ununseptium is harmful due to its radioactivity.


Ununseptium is a synthetic radioactive metal and has only been produced in minute amounts.

Uses of Ununseptium

Ununseptium is of research interest only.

Abundance and Isotopes

Abundance earth’s crust: nil

Abundance solar system: parts per trillion by weight, parts per trillion by moles

Cost, pure: $ per 100g

Cost, bulk: $ per 100g

Source: Data from the discovery teams suggest ununseptium may be produced by bombarding 249Bk with 48Ca in a heavy ion accelerator.

Isotopes: Initial data has identified 2 isotopes of ununseptium, with mass numbers 293 and 294. Neither are stable. Ununseptium-293’s approximate half-life is 14 ms and ununseptium-294’s is 78 ms.


1. Yu. Ts. Oganessian et al., Phys. Rev. Lett., 2010, 104, 142502, 4 pages.
2. Office of Science, Nations Work Together to Discover New Element,.
3. Press Release The Armenia Weekly.

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