oganesson
What is oganesson?
How did oganesson get its name?
What is oganesson used for?
Why is oganesson so rare?
When was oganesson first synthesized?
oganesson (Og), a synthetic transuranium element with the atomic number 118 that is a member of the noble gases, or Group 18 (VIIIA), of the periodic table. First synthesized in 2002, it is the heaviest element yet produced and is highly radioactive, with isotopes that decay in less than a millisecond. The extremely short half-life of the few synthesized atoms has severely limited experimental data, and its chemical and physical properties have therefore been theoretically predicted rather than empirically determined. Oganesson is formally classified as a noble gas based on its atomic number and position in the modern periodic table; however, it is predicted to differ from the lighter noble gases in reactivity, electrical conductivity, and physical state.
| atomic number | 118 |
|---|---|
| atomic weight | 294 |
| electron configuration | (Rn)5f146d107s27p6 |
Discovery and recognition
In 1999 scientists at Lawrence Berkeley National Laboratory in Berkeley, California, announced the production of atoms of oganesson as a result of the bombardment of lead-208 with atoms of krypton-86. However, in 2001 this result was retracted after it was discovered that some of the data had been falsified.
In 2006 scientists at the Joint Institute for Nuclear Research at Dubna, Russia, announced that oganesson had been made in 2002 and 2005 in a cyclotron by the nuclear reaction of calcium-48 at an energy of 245 million electron volts (MeV) with a californium-249 target, with three neutrons and one atom of oganesson as the reaction products. Nearly a millisecond after creation, the oganesson nucleus decays into another transuranium element, livermorium, by emitting an alpha particle (helium nucleus).
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In late 2015 the discovery of element 118 was recognized by the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics. The discoverers named it oganesson for Russian physicist Yuri Oganessian, who led the group at Dubna that discovered it and several of the other heaviest transuranium elements. The name oganesson was approved by IUPAC in November 2016.
Relativistic effects and half-life
With 118 protons, oganesson has an extremely high nuclear charge that pulls its electrons inward so strongly that they move almost as fast as light. At such a speed, relativistic effects become pronounced: When electrons move at a significant fraction of the speed of light, their effective mass increases, altering the atom’s electronic structure and therefore its properties.
Because only a few atoms of oganesson have been synthesized and its properties cannot be directly measured, its behavior has been inferred from calculations that take these relativistic effects into account. Oganesson would be more reactive than helium, neon, or argon and solid at room temperature, with a calculated melting point of about 325 K—unlike the other noble gases, which are gaseous under the same conditions. In the solid state, oganesson would have a band gap (the energy required to move an electron so that it can conduct electricity) of roughly 1.5 electron volts—far smaller than those of other noble gases—indicating semiconductor rather than insulating behavior.
The longest-lived known isotope, oganesson-294, has an estimated half-life (the time required for half of the radioactive atoms to decay into a more stable form) of less than a millisecond. Because it exists for such a brief time and can be produced only in particle accelerators, oganesson has no established practical applications beyond scientific research.
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