roentgenium

colspan=2 align=center bgcolor="#ffc0c0" \|Known properties
colspan=2 align=center\|darmstadtium – roentgenium – ununbium
a href="/encyclopedia/Gold" title="Gold">Au Rg	rowspan=3 align=center\| Full table	}
a href="/encyclopedia/List-of-elements-by-name" title="List of elements by name">Name, Symbol, Number	roentgenium, Rg, 111
a href="/encyclopedia/Chemical-series" title="Chemical series">Chemical series	Transition metals
a href="/encyclopedia/periodic-table-group" title="periodic table group">Group, Period, Block	11, 7, d
a href="/encyclopedia/color" title="color">Appearance	unknown; probably metallic, silvery white or gray
a href="/encyclopedia/Atomic-weight" title="Atomic weight">Atomic weight	[272] amu
a href="/encyclopedia/Electron-configuration" title="Electron configuration">Electron configuration	probably [Rn]5f¹⁴ 6d¹⁰ 7s¹
a href="/encyclopedia/electron" title="electron">e^- 's per energy level	2, 8, 18, 32, 32, 17, 2
a href="/encyclopedia/State-of-matter" title="State of matter">State of matter	Presumably a solid

Roentgenium (former temporary name: unununium or eka-gold) is a chemical element in the periodic table that has the symbol Rg (formerly temporarily Uuu) and atomic number 111. It has an atomic weight of 272 making it one of the super-heavy atoms. It is a synthetic element whose only known isotope has a half-life of around 15 ms before it decays into meitnerium. Due to its presence in Group 11 it is a transition metal and so probably metallic and solid.

History

It was first created at the Gesellschaft fr Schwerionenforschung (GSI) in Darmstadt, Germany on December 8, 1994. Only three atoms of it have been created (all ²⁷²Rg), by the fusion of bismuth-209 and nickel-64 in a linear accelerator. (Nickel was bombarded onto the target.) The name roentgenium was accepted as a permanent name on November 1 2004 in honour of Wilhelm Roentgen; before this date, the element was known under the temporary IUPAC systematic element name unununium. Some research has referred to it as "eka-gold".

Isotopes

Three isotopes of roentgenium are known. The longest-lived of these is ²⁸⁰Rg which decays through alpha decay and has a half-life of 3.6 s. the shortest-lived isotope is ²⁷²Rg which decays through alpha decay and has a half life of 1.5 ms. The other known isotope; ²⁷⁹Rg decays through alpha decay and has a half-life of 170 ms.

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