• synonyms


[yoo-nil-hek-see-uh m]
noun Chemistry, Physics.
  1. former name of seaborgium. Symbol: Unh
Show More

Origin of unnilhexium

1975–80; < Latin ūn(us) one + nīl nothing + Greek héx six + New Latin -ium -ium
Also called element 106.


[see-bawr-gee-uh m, see-bawr-]
noun Chemistry, Physics.
  1. a superheavy, synthetic, radioactive element with a very short half-life. Symbol: Sg; atomic number: 106.
Show More

Origin of seaborgium

named after U.S. chemist Glenn T. Seaborg; see -ium
Formerly unnilhexium, element 106.

element 106

noun Chemistry, Physics.
  1. seaborgium.
Show More

Origin of element 106

First recorded in 1975–80
Formerly unnilhexium.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for unnilhexium


  1. a synthetic transuranic element, synthesized and identified in 1974. Symbol: Sg; atomic no: 106
Show More

Word Origin

C20: named after Glenn Seaborg
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

unnilhexium in Science


  1. A synthetic, radioactive element that is produced by bombarding californium with oxygen ions or bombarding lead with chromium ions. Its most long-lived isotopes have mass numbers 259, 261, 263, 265, and 266 with half-lives of 0.9, 0.23, 0.8, 16, and 20 seconds, respectively. Atomic number 106. See Periodic Table.
Show More
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.