U1Un

U1Un, also known as Ununoctium, is a chemical element with the symbol Uuo and atomic number 118. It is the heaviest known element and is classified as a transactinide element in the periodic table. U1Un is a synthetic element, meaning it does not occur naturally and must be created in a laboratory setting.

The discovery of U1Un was announced in 2002 by a team of scientists from the Joint Institute for Nuclear Research in Dubna, Russia, and the Lawrence Livermore National Laboratory in California, USA. The element was synthesized by bombarding californium-249 with calcium-48 ions, resulting in the creation of a few atoms of U1Un. Due to its extremely short half-life and the difficulty in producing it, much of the properties of U1Un remain unknown.

U1Un is expected to be a noble gas under standard conditions, similar to other elements in its group, such as radon and xenon. However, due to relativistic effects, its properties may differ significantly from those of its lighter homologs. The exact placement of U1Un in the periodic table is also a subject of debate among scientists, with some suggesting it may belong to a new period or group.

The name "Ununoctium" is a temporary systematic element name derived from the digits of its atomic number, 118. The International Union of Pure and Applied Chemistry (IUPAC) has not yet officially recognized the discovery of U1Un, and a permanent name and symbol have not been assigned. The discovery and synthesis of U1Un represent significant advancements in the field of nuclear physics and the understanding of the periodic table.