Zirconium

40 yttrium ← zirconium → niobium Ti ↑ Zr ↓ Hf 250px Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	zirconium, Zr, 40
Chemical series	transition metals
Group, Period, Block	4, 5, d
Appearance	silvery white File:Zr,40.jpg
Standard atomic weight	91.224(2)  g·mol−1
Electron configuration	[Kr] 4d2 5s2
Electrons per shell	2, 8, 18, 10, 2
Physical properties
Phase	solid
Density (near r.t.)	6.52  g·cm−3
Liquid density at m.p.	5.8  g·cm−3
Melting point	2128 K (1855 °C, 3371 °F)
Boiling point	4682 K (4409 °C, 7968 °F)
Heat of fusion	14  kJ·mol−1
Heat of vaporization	573  kJ·mol−1
Heat capacity	(25 °C) 25.36  J·mol−1·K−1
Vapor pressure P(Pa) 1 10 100 1 k 10 k 100 k at T(K) 2639 2891 3197 3575 4053 4678
Atomic properties
Crystal structure	hexagonal close-packed
Oxidation states	4, 3, 2, 1, (amphoteric oxide)
Electronegativity	1.33 (scale Pauling)
Ionization energies (more)	1st:  640.1  kJ·mol−1
	2nd:  1270  kJ·mol−1
	3rd:  2218  kJ·mol−1
Atomic radius	155  pm
Atomic radius (calc.)	206  pm
Covalent radius	148  pm
Miscellaneous
Magnetic ordering	no data
Electrical resistivity	(20 °C) 421 n Ω·m
Thermal conductivity	(300 K) 22.6  W·m−1·K−1
Thermal expansion	(25 °C) 5.7  µm·m−1·K−1
Speed of sound (thin rod)	(20 °C) 3800 m/s
Young's modulus	68  GPa
Shear modulus	33  GPa
Poisson ratio	0.34
Mohs hardness	5.0
Vickers hardness	903  MPa
Brinell hardness	650  MPa
CAS registry number	7440-67-7
Selected isotopes
iso NA half-life DM DE (MeV) DP 88Zr syn 83.4 d ε - 88Y γ 0.392D - 89Zr syn 78.4 h ε - 89Y β+ 0.902 89Y γ 0.909D - 90Zr 51.45% Zr is stable with 50 neutrons 91Zr 11.22% Zr is stable with 51 neutrons 92Zr 17.15% Zr is stable with 52 neutrons 93Zr syn 1.53×106y β− 0.060 93Nb 94Zr 17.38% Zr is stable with 54 neutrons 96Zr 2.8% 2.0×1019y β−β− 3.348 96Mo
References

Zirconium (pronounced /zɚˈkoʊniəm/, /ˌzɝˈkoʊniəm/) is a chemical element that has the symbol Zr and has the atomic number 40. A lustrous, very corrosion resistant, gray-white, strong transition metal that resembles titanium, zirconium is obtained mainly from the mineral zircon. Zirconium is primarily used in nuclear reactors, especially in the cladding of the fuel rods, due to its low neutron-capture cross-section and its resistance to corrosion.

Characteristics

Zirconium is a grayish-white metal, lustrous, and quite corrosion-resistant. Zirconium is lighter than steel and its hardness is similar to copper. When it is finely divided into a powder, zirconium can spontaneously ignite in air, especially at high temperatures. (It is much more difficult to ignite the solid metal.) The Zirconium-zinc alloy becomes magnetic at temperatures below 35 K. The oxidation state of zirconium is usually +4, although +3 and +2 can also be obtained inside of chemical compounds.

History

Zirconium (from Syriac zargono, Arabic zarkûn from Persian zargûn زرگون meaning "gold like") was discovered in 1789 by Martin Heinrich Klaproth, isolated in 1824 by Jöns Jakob Berzelius, and finally put in a pure form in 1914.

The zirconium-containing mineral zircon, or its variations (jargon, hyacinth, jacinth, or ligure), were mentioned in biblical writings. The mineral was not known to contain a new element until Klaproth analyzed a jargon (what's a 'jargon' -- no answer in WK) from the island of Ceylon in the Indian Ocean. He named the new element Zirkonertz (zirconia). The impure metal was isolated first by Berzelius by heating a mixture of potassium and potassium-zirconium fluoride in a small decomposition process conducted in an iron tube. Pure zirconium wasn't prepared until 1914.

The crystal bar process (or Iodide process), discovered by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925, was the first industrial process for the commercial production of pure metallic zirconium. It was later superseded by the Kroll process.

Occurrence

File:2005zirconium.PNG

Zirconium output in 2005

File:Zirconium mineral concentrates - world production trend.svg

World production trend of zirconium mineral concentrates

Zirconium is never found in nature as a native metal. The principal economic source of zirconium is the zirconium silicate mineral, zircon (ZrSiO₄), which is found in deposits located in Australia, South Africa and the United States, as reported by the British Geological Survey. It is extracted either as a dark sooty powder, or as a gray metallic crystalline substance. Zirconium and hafnium are contained in zircon at a ratio of about 50 to 1, and they are quite difficult to separate chemically. Zircon is a co-product or by-product of the mining and processing of heavy-mineral sands for the titanium minerals, ilmenite and rutile, or from tin minerals. Zirconium also occurs in about 30 other recognized mineral species including baddeleyite. This metal is commercially produced mostly by the reduction of the zirconium(IV) chloride with magnesium metal in the Kroll process. Commercial-quality zirconium for most uses still has a content of 1% to 3% hafnium.

This element is relatively-abundant in S-type stars, and it has been detected in the sun and in meteorites. Lunar rock samples brought back from several Apollo program missions to the moon have a quite high zirconium oxide content relative to terrestrial rocks.

See also zirconium minerals.

Isotopes

Naturally-occurring zirconium is composed of four stable isotopes, and one extremely long-lived radioisotope (⁹⁶Zr). The second most stable radioisotope is ⁹³Zr which has a half-life of 1.53 million years. Eighteen other radioisotopes have been observed. Most of these have half-lives that are less than a day except for ⁹⁵Zr (64.02 days), ⁸⁸Zr (63.4 days), and ⁸⁹Zr (78.41 hours). The primary decay mode is electron capture for isotopes lighter than ⁹²Zr, and the primary mode for heavier isotopes is beta decay. Other isotopes of zirconium include ⁹⁰Zr, ⁹¹Zr, and ⁹⁴Zr

Compounds

Some common zirconium compounds are: ZrC, ZrO₂, ZrN, ZrCl₄, ZrS₂, ZrSi₂, ZrSiO₄, ZrF₄, ZrBr₄, ZrI₄, Zr(OH)₄, C₁₀H₁₁ClZr, Zr(CH₃CH₂COO)₄, Zr(WO₄)₂, ZrH₂, Pb(Zr_xTi_1-x)O₃

Precautions

File:Zirconium rod.jpg

Zirconium rod

Compounds containing zirconium are not noted for toxicity. The metal dust can ignite in air and should be regarded as a major fire and explosion hazard. Zirconium has no known biological role.

References

• Los Alamos National Laboratory – Zirconium

External links

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Zirconium

Look up zirconium in
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• WebElements.com – Zirconiumaf:Sirkonium