Stories We Like: A Guide to the Comma


[yoo-nil-hek-see-uh m] /ˌyu nɪlˈhɛk si əm/
noun, Chemistry, Physics.
former name of seaborgium. Symbol: Unh.
Also called element 106.
1975-80; < Latin ūn(us) one + nīl nothing + Greek héx six + Neo-Latin -ium -ium Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source
Encyclopedia Article for unnilhexium


an artificially produced radioactive element in Group VIb of the periodic table, atomic number 106. In June 1974, Georgy N. Flerov of the Joint Institute for Nuclear Research at Dubna, Russia, U.S.S.R., announced that his team of investigators had synthesized and identified element 106. In September of the same year, a group of American researchers headed by Albert Ghiorso at the Lawrence Radiation Laboratory (now Lawrence Berkeley Laboratory) of the University of California at Berkeley reported their synthesis of the identical element. Disagreement arose between the two groups over the results of their experiments, both having used different procedures to achieve the synthesis. The Soviet scientists had bombarded lead-207 and lead-208 with ions of chromium-54 to produce an isotope of element 106 having a mass number of 259 and decaying with a half-life of approximately 0.007 second. The American researchers, on the other hand, had bombarded a heavy radioactive target of californium-249 with projectile beams of oxygen-18 ions, which resulted in the creation of a different isotope of element 106-one with a mass number of 263 and a half-life of 0.9 second. Russian researchers at Dubna reported their synthesis of two isotopes of the element in 1993, and a team of researchers at Lawrence Berkeley duplicated the Ghiorso group's original experiment that same year. In honour of the American nuclear chemist Glenn T. Seaborg, American researchers tentatively named the element seaborgium, which was later ratified by the International Union of Pure and Applied Chemistry. Based on its position in the periodic table, seaborgium is thought to have chemical properties akin to those of tungsten.

Learn more about Sg with a free trial on
Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
Cite This Source

Word of the Day

Difficulty index for unnilhexium

Few English speakers likely know this word

Word Value for unnilhexium

Scrabble Words With Friends

Nearby words for unnilhexium