n. (Symbol Rg)
An artificially produced radioactive element with atomic number 111 and a mass number of 280, whose most stable known isotope has a half-life of 3.6 seconds.
[After Wilhelm Konrad ROENTGEN.]
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
