a soft silvery
atomic weight 178.49 amu
3,902º F (2,150º C)
boiling point 9,752º F (5,400º
number of stable
Hafnium metal is silver in
color, but usually appears gray because of an
oxide layer that forms when the metal is exposed
to the air.
Hafnium powder can ignite
spontaneously in air.
Hafnium can be alloyed with
iron, niobium, tantalum, and many other elements.
Hafnium is resistant to
concentrated alkalis, but at high temperatures
reacts readily with oxygen, nitrogen, carbon, boron, sulfur, and silicon.
Hafnium is never found as a
free element in nature. Most zirconium minerals
contain 1 to 3% hafnium, and most hafnium is
produced as a byproduct of zirconium production.
Hafnium is used for nuclear reactor control
rods because of its ability to absorb neutrons
and its good mechanical and corrosion resistance
qualities. It is also used as a filament in
photographic flash bulbs and
gas-filled and incandescent lamps, as well as in
cathodes, capacitors, and other electronic
Hafnium oxide compounds are
used in some silicon chips in order to produce
smaller processors with improved energy
efficiency. Hafnium-niobium alloys are used in
many aerospace applications, including space
rocket engines, and hafnium carbide is used to
line high temperature furnaces and kilns.
Russian chemist Dmitri
Mendeleyev predicted the existence of
"element 72" in 1869. Georges Urbain
thought he had discovered that element, which he
called celtium, in 1911, but his
discovery was later found to a mixture of
previously known elements. In 1921, Neils Bohr
suggested that Hungarian radiochemist George von
Hevesy look for the element in zirconium ores.
Hevesy teamed with Danish chemist Dirk Coster,
and the two discovered hafnium in 1923. The men
took the element's name from Hafnia, the
Latin word for Copenhagen, the city
where it was discovered and the capital of
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