Ununnilium is a metal in Group VIIIB and the 7th period. It is a synthetic element; none occurs naturally on earth.
The element was discovered by Oganessian, et al., in 1987. The name Ununnilium and the symbol Uun are both temporary names suggested by the IUPAC.
Uun is synthetic, just as are are all other elements beyond U. It has been made by bombarding lead for many days with Nickle atoms.
272Uun has a half-life of 10 milliseconds.
Only a few atoms of Uun have ever been made, and these atoms only exist for a fraction of a second, so little is known about the chemistry of the element.