roentgenium

[ rent-gen-ee-uhm, -jen-, ruhnt- ]
/ rɛntˈgɛn i əm, -ˈdʒɛn-, rʌnt- /

noun Chemistry, Physics.

a superheavy, synthetic radioactive element with a very short half-life. Symbol: Rg; atomic number: 111.

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Formerly u·nu·nun·i·um [uh-nuh-nuhn-ee-uhm] /ə nəˈnʌn i əm/ , el·e·ment 111 .

Origin of roentgenium

First recorded in 2000–05; named after German physicist Wilhelm Konrad Roentgen. Its former name, unununium, came from Latin ūn(us) “one” + Latin ūn(us) + Latin ūn(us) + -ium; see origin at one, -ium
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Scientific definitions for roentgenium

roentgenium
[ rĕnt-gĕnē-əm, -jĕn-, rŭnt-, rœnt-gĕn- ]

Rg

An artificially produced radioactive element with a mass number of 280. Its most stable known isotope has a half-life of 3.6 seconds. Atomic number 111. See Periodic Table.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.