hafnium

[haf-nee-uhm, hahf-]
noun Chemistry.
a gray, toxic metallic element with a high melting point (over 2000°C), found in most zirconium minerals. Symbol: Hf; atomic weight: 178.49; atomic number: 72; specific gravity: 12.1.

Origin:
1923; < Neo-Latin Hafn(ia) Copenhagen + -ium

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source Link To hafnium
Collins
World English Dictionary
hafnium (ˈhæfnɪəm)
 
n
a bright metallic element found in zirconium ores: used in tungsten filaments and as a neutron absorber in nuclear reactors. Symbol: Hf; atomic no: 72; atomic wt: 178.49; valency: 4; relative density: 13.31; melting pt: 2231±20°C; boiling pt: 4603°C
 
[C20: New Latin, named after Hafnia, Latin name of Copenhagen + -ium]

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
Cite This Source
American Heritage
Medical Dictionary

hafnium haf·ni·um (hāf'nē-əm)
n.
Symbol Hf
A metallic element found with zirconium and used in nuclear reactor control rods and in tungsten alloys used in filaments. Atomic number 72; atomic weight 178.49; melting point 2,230°C; boiling point 4,600°C; specific gravity 13.3; valence 4.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Cite This Source
American Heritage
Science Dictionary
hafnium   (hāf'nē-əm)  Pronunciation Key 
Symbol Hf
A bright, silvery metallic element that occurs in zirconium ores. Because hafnium absorbs neutrons better than any other metal and is resistant to corrosion, it is used to control nuclear reactions. Atomic number 72; atomic weight 178.49; melting point 2,220°C; boiling point 5,400°C; specific gravity 13.3; valence 4. See Periodic Table.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
Cite This Source
Encyclopedia Britannica
Encyclopedia

hafnium

chemical element (atomic number 72), metal of Group IVb of the periodic table. It is a ductile metal with a brilliant silvery lustre. The Dutch physicist Dirk Coster and the Hungarian-Swedish chemist George Charles de Hevesy discovered (1923) hafnium in Norwegian and Greenland zircons by analyzing their X-ray spectra. They named the new element for Copenhagen (in New Latin, Hafnia), the city in which it was discovered. Hafnium is dispersed in the Earth's crust to the extent of three parts per million and is invariably found in zirconium minerals up to a few percent compared with zirconium. Altered zircons, like some alvites and cyrtolites, products of residual crystallization, show greater percentages of hafnium (up to 17 percent hafnium oxide in cyrtolite from Rockport, Mass., U.S.). Commercial sources of hafnium-bearing zirconium minerals are found in beach sands and river gravel in the United States (principally Florida), Australia, Brazil, western Africa, and India. Hafnium vapour has been identified in the Sun's atmosphere.

Learn more about hafnium with a free trial on Britannica.com.

Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
Cite This Source
Example sentences
Hafnium is used in nuclear control rods because of its high thermal neutron absorption cross section.
The job of such a precursor compound is to deliver a metal atom, such as hafnium, to the surface of a hot silicon wafer.
In the top photo, the small size of the hafnium beads is illustrated next to a penny.
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature