a soft silvery metallic element

Properties

atomic number 72
atomic weight 178.49 amu

melting point 3,902º F (2,150º C)
boiling point 9,752º F (5,400º C)

number of stable isotopes 5

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.

Sources

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.

Uses

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 equipment.

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.

History

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 Denmark.

Carbon
Boron
Sulfur
Silicon

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