Roentgenium

General properties
Name, symbol, number	roentgenium, Rg, 111
Element category	unknown but probably a transition metal
Group, period, block	11, 7, d
Standard atomic weight	(281)
Electron configuration	[Rn] 5f14 6d9 7s2 (predicted) 2, 8, 18, 32, 32, 17, 2 (predicted)
History
Discovery	Gesellschaft für Schwerionenforschung (1994)

Roentgenium is a chemical element with the symbol Rg and atomic number 111. It is an extremely radioactive synthetic element (an element that can be created in a laboratory but is not found in nature); the most stable known isotope, roentgenium-281, has a half-life of 26 seconds. Roentgenium was first created in 1994 by the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany. It is named after the physicist Wilhelm Röntgen (also spelled Roentgen).

In the periodic table, it is a d-block transactinide element. It is a member of the 7th period and is placed in the group 11 elements, although no chemical experiments have been carried out to confirm that it behaves as the heavier homologue to gold in group 11. Roentgenium is calculated to have similar properties to its lighter homologues, copper, silver, and gold, although it may show some differences from them.

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