Rg, or roentgenium, is a synthetic element with the atomic number 111. It was first created in 1994 by a team of Russian and American scientists at the Joint Institute for Nuclear Research in Dubna, Russia. Rg is highly radioactive and has no stable isotopes, with its most stable isotope, Rg-282, having a half-life of about 2.1 milliseconds. Due to its short half-life, Rg does not occur naturally and is produced in particle accelerators through nuclear reactions. Its properties are not well-studied, but it is expected to be a metal and may share characteristics with other elements in the group 11 of the periodic table, such as gold and silver.