Zirconium

yttrium – zirconium – niobium Ti Zr Hf    Missing image Zr-TableImage.png Image:Zr-TableImage.png Full table
General
Name, Symbol, Number	Zirconium, Zr, 40
Chemical series	transition metals
Group, Period, Block	4, 5, d
Density, Hardness	6511 kg/m3, 5
Appearance	Silvery white
Atomic properties
Atomic weight	91.224 amu
Atomic radius (calc.)	155 (206) pm
Covalent radius	148 pm
van der Waals radius	no data
Electron configuration	[Kr]4d25s2
e- 's per energy level	2, 8, 18, 10, 2
Oxidation states (Oxide)	4 (amphoteric)
Crystal structure	Hexagonal
Physical properties
State of matter	Solid (__)
Melting point	2128 K (3371 ?F)
Boiling point	4682 K (7968 ?F)
Molar volume	14.02 ×10-6 m3/mol
Heat of vaporization	58.2 kJ/mol
Heat of fusion	16.9 kJ/mol
Vapor pressure	0.00168 Pa at 2125 K
Speed of sound	3800 m/s at 293.15 K
Miscellaneous
Electronegativity	1.33 (Pauling scale)
Specific heat capacity	0.27 J/(kg*K)
Electrical conductivity	2.36 106/(m&middotohm)
Thermal conductivity	22.7 W/(m*K)
1st ionization potential	640.1 kJ/mol
2nd ionization potential	1270 kJ/mol
3rd ionization potential	2218 kJ/mol
4th ionization potential	3313 kJ/mol
5th ionization potential	7752 kJ/mol
6th ionization potential	9500 kJ/mol
Most stable isotopes
iso NA half-life DM DE MeV DP 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 E6 y β- 0.091 93Nb 94Zr 17.38% Zr is stable with 54 neutrons 96Zr 2.8% >3.8 E19 y β- 3.350 96Mo
SI units & STP are used except where noted.

Zirconium is a chemical element in the periodic table that has the symbol Zr and atomic number 40. A lustrous gray-white, strong transition metal that resembles titanium, zirconium is obtained chiefly from zircon and is very corrosion resistant. Zirconium is primarily used in nuclear reactors for a neutron absorber and to make corrosion-resistant alloys.

Contents

1 Notable characteristics 2 Applications 3 History 4 Occurrence 5 Isotopes 6 Precautions 7 References

Notable characteristics

It is a grayish-white metal, lustrous and exceptionally corrosion resistant. Zirconium is lighter than steel and its hardness is similar to copper. When it is finely divided, the metal can spontaneously ignite in air, especially at high temperatures (it is much more difficult to ignite the solid metal). Zirconium zinc alloy becomes magnetic at temperatures below 35° K. Oxidation states of zirconium include +4, although +3 and +2 can be obtained.

Applications

The major end uses of zircon (ZrSiO₄) are refractories, foundry sands (including investment casting), and ceramic opacification. Zircon is also marketed as a natural gemstone used in jewelry, and its oxide is processed to produce the diamond simulant, cubic zirconia. Other uses:

• Zirconium has a low absorption cross section for neutrons, which makes it ideal for nuclear energy uses, such as cladding fuel elements. More than 90% of zirconium metal production is consumed by commercial nuclear power generation. Modern commercial scale reactors can use as much as a 150,000 meters of zirconium alloy tubing.
• Extensively used by the chemical industry for piping in corrosive environments.
• Zirconium is pyrophoric (flammable) and has been used in military incendiaries.
• Its carbonate is used in poison ivy lotions.
• Impure zirconium oxide, zirconia, is used to make laboratory crucibles that can withstand heat shock, for linings of metallurgical furnaces, and by the ceramic and glass industries as a refractory material.
• Human tissues can easily tolerate this metal which makes it suitable for some artificial joints and limbs.
• Also used in heat exchangers, as a "getter" in vacuum tubes, in lamp filaments and various specialty alloys.
• When alloyed with niobium, zirconium becomes superconductive at low temperatures and is used to make superconductive magnets with possible large-scale electrical power uses.
• Zirconium Diamide-Diamine complexes can be used to catalyse the polymerisation of alkenes, especially ethene, when activated with Trityl-BArF.

History

Zirconium (Arabic zark?from Persian zarg?meaning "gold like") was discovered in 1789 by Martin Heinrich Klaproth and isolated in 1824 by J?Jakob Berzelius.

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 from 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.

Occurrence

Zirconium is never found in nature as a free metal. The principal economic source of zirconium is the zirconium silicate mineral, zircon (ZrSiO₄), which is found in deposits located in Australia, Brazil, India, Russia, and the United States. (It is extracted 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 are difficult to separate. Zircon is a coproduct or byproduct of the mining and processing of heavy-mineral sands for the titanium minerals, ilmenite and rutile, or tin minerals. Zirconium is also in 30 other recognized mineral species including baddeleyite. This metal is commercially produced by reduction of the Zirconium(IV) chloride with magnesium in the Kroll process, and through other methods. Commercial-quality zirconium still has a content of 1 to 3% hafnium.

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

Isotopes

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

Precautions

Compounds containing zirconium are encountered relatively rarely by most people and their inherent toxicity is low. The metal dust can ignite in air and should be regarded as a major fire and explosion hazard. Zirconium has no biological role. Template:Chem clipart

References

• Los Alamos National Laboratory – Zirconium (http://pearl1.lanl.gov/periodic/elements/40.html)