Zirconium
Symbol: Zr
Atomic Number: 40
Atomic Mass: 91.224 amu (atomic mass units)
Melting Point: 1852.0 C (2125.15 K, 3365.6 F)
Boiling Point: 4377.0 C (4650.15 K, 7910.6 F)
Number of Protons: 40
Number of Electrons: 40
Number of Neutrons: 51
Classification: Transition Metal
Crystal Structure: Hexagonal
Density @ 293 K: 6.49 grams per cubic centimeter
Color: Gray
Zirconium was discovered by the German chemist Martin Heinrich Klaproth in 1789. He found it while making an examination of a sample of the mineral jargon. It was isolated in an impure form in 1824 by Jons Jacob Berzelius when he heated a mixture of potassium and potassium zirconium fluoride in an iron tube. Pure zirconium metal was eventually produced in 1914. Even today preparing pure zirconium is a difficult process. Most minerals containing zirconium also contain the chemically similar element hafnium and commercial grade zirconium usually contains a small percentage of hafnium. It is usually obtained, via the Kroll Process of reduction with potassium or sodium, from the minerals zircon and baddyeleyte.
The name Zirconium comes from the Persian word “Zargun” meaning gold colored and describes the color of the zirconium containing gemstone Zircon. Minerals containing this element such as jargon, hyacinth and jacinth have been known for many thousands of years and are actually mentioned in the bible.
The solid metal has a lustrous grayish-white appearance. If the metal is finely divided it can ignite spontaneously in air particularly at higher temperatures. However the solid metal is much harder to ignite.
Zirconium has a number of industrial uses. Zirconium does not absorb neutrons very easily and so the major user of the element in the world today is the nuclear power industry where it forms a vital part of the nuclear reactors. The zirconium used in the nuclear power industry is of a higher grade than the commercial grade and is virtually free of hafnium contamination. Zirconium also resists corrosion and has a use in high performance valves and pumps. Many surgical appliances are made of alloys of zirconium.
Many zirconium compounds also have uses. Zirconium dioxide is very heat resistant and is used to manufacture crucibles. Treatments for persons who have come into contact with poison ivy often contain zirconium carbonate. Jewelry is made from Zircon which is a mineral containing zirconium silicon oxide. Zircon can be cut and polished to resemble diamonds.
The element is found throughout the universe. Spectroscopic analysis of the light from S-type stars has shown that they contain zirconium. It is also commonly found in meteorites. The lunar rocks bought back to earth by the Apollo missions have shown that the moon has a higher abundance of zirconium than the earth.
