40
  Zr  
91.224000
Zirconium

Name: Zirconium
Symbol: Zr
Atomic Number: 40
AtomicWeight: 91.224000
Family: Transition Metals
CAS RN: 7440-67-7
Description: A hard rare grayish-white metal, which is resistant towards corrosion due to an oxide film on its surface. It will burn in air if ignited.
State (25 C): Solid
Oxidation states: +4

Molar Volume: 14.06 cm3/mole
Valence Electrons: 4d25s2

Boiling Point:  4650K, 4377C, 7911F
Melting Point:
2125K, 1852C, 3366F
Electrons Energy Level: 2, 8, 18, 10, 2
Isotopes: 28 + 4 Stable
Heat of Vaporization: 58.2 kJ/mol
Heat of Fusion: 16.9 kJ/mol
Density: 6.51 g/cm3 @ 300K
Specific Heat: 0.27 J/gK
Atomic Radius: 2.16
Ionic Radius: 0.72
Electronegativity: 1.33 (Pauling); 1.22 (Allrod Rochow)
Vapor Pressure: 0.00168 Pa @ 1852C

1s2 2s2p6 3s2p6d10 4s2p6d2 5s2

History

Zirconium (Arabic zarkn from Persian  zargn meaning "gold like") was discovered in 1789 by Martin Heinrich Klaproth and isolated in 1824 by Jons Jakob Berzelius.

180px-Martin_Heinrich_Klaproth.jpg (7368 bytes)

Martin Heinrich Klaproth

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.

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 ductile metallic zirconium.  It was superseded by the Kroll process.

Characteristics

Zirconium is a grayish-white metal, lustrous and exceptionally corrosion resistant that resembles titanium, zirconium is obtained chiefly from zircon and is very 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 35oK.  Oxidation state of zirconium is usually +4, although +3 and +2 can also be obtained.

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d2
5s2

Zirconium is primarily used in nuclear reactors due to its resistance to corrosion and low neutron cross-section.

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 meterorites.  Lunar rock samples brought back from several Apollo progrm missions to the moon have a very high zirconium oxide content relative to terrestrial rocks.

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, oxide is processed to produce Cubic Zirconia, ZrO2, which forms a brilliant clear crystal used as a low-cost substitute for diamond.

Other Uses

Hafnium-Free Zirconium

Reactor-grade zirconium alloys must be made of purified zirconium free of hafnium contamination, as hafnium has very high neutron absorption cross-section, 600 times higher than zirconium.  Commercial zirconium naturally contains 1-5% of hafnium which has to be removed.  This removal process is difficult (zirconium and hafnium are two of the most difficult elements to separate).  Two main process are in use: liquid-liquid extraction, exploiting the difference of solubility of metal thiocyanates in methyl isobutyl ketone, used mainly in United States, and extractive distillation, used primarily in Europe.  The resulting reactor-grade zirconium is about 10 times as expensive as the hafnium-contaminated commercial grade.  The separated hafnium is used for control rods.  The zirconium is used mostly almost pure, in the form of low alloys, most often from the zircaloy group.

Compounds

Zircon, Zirconium Silicate, ZrSiO4
Zirconium (IV) Chloride, ZrCl4
Baddeleyite, Cubic Zirconia, Zirconium Dioxide, ZrO2
Zirconium Carbonate, 3ZrO2CO2H2O

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.   Twenty-eight other radioisotopes have been characterized.  Most of these have half lives that are less than a day except 95Zr (64.02 days), 88Zr (63.4 days), and 89Zr (78.41 hours).  The primary decay mode is electron capture before 92Zr and the primary mode after is beta decay.

atom.gif (700 bytes)

Isotope Atomic Mass Half-Life
Zr79 78.949 56 ms
Zr80 79.941 3.9 seconds
Zr81 80.937 15 seconds
Zr82 81.931 32 seconds
Zr83 82.929 44 seconds
Zr84 83.923 25.9 minutes
Zr85 84.921 7.86 minutes
Zr86 85.9165 16.5 hours
Zr87 86.9148 1.68 hours
Zr88 87.9102 83.4 days
Zr89 88.9089 78.41 hours
Zr90 89.9047 Stable
Zr91 90.9057 Stable
Zr92 91.905 Stable
Zr93 92.9065 1,530,000 years
Zr94 93.9063 Stable
Zr95 94.908 64.02 days
Zr96 95.9083 >3.8E 19 years
Zr97 96.911 16.91 hours
Zr98 97.9127 30.7 seconds
Zr99 98.9165 2.1 seconds
Zr100 99.9178 7.1 seconds
Zr101 100.9211 2.3 seconds
Zr102 101.923 2.9 seconds
Zr103 102.927 1.3 seconds
Zr104 103.929 1.2 seconds
Zr105 104.933 0.6 seconds
Zr106 105.936 >150 ns
Zr107 106.941 >150 ns
Zr108 107.944 80 ms
Zr109   > 150 ns
Zr110   > 150 ns

Precautions

80px-Flammable.jpg (2186 bytes) 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 biological role.

atom.gif (700 bytes)

Zirconium Data
 

Atomic Structure

  • Atomic Radius: 2.16
  • Atomic Volume: 14.1cm3/mol
  • Covalent Radius: 1.45
  • Cross Section (Thermal Neutron Capture) Barns: 0.184
  • Crystal Structure: Hexagonal
  • Electron Configuration:
    1s2 2s2p6 3s2p6d10 4s2p6d2 5s2
  • Electrons per Energy Level: 2, 8, 18, 10, 2
  • Ionic Radius: 0.72
  • Filling Orbital: 4d2
  • Number of Electrons (with no charge): 40
  • Number of Neutrons (most common/stable nuclide): 51
  • Number of Protons: 40
  • Oxidation States: 4
  • Valence Electrons: 4d2 5s2

Chemical Properties

  • Electrochemical Equivalent: 0.8509 g/amp-hr
  • Electron Work Function: 4.05eV
  • Electronegativity: 1.33 (Pauling); 1.22 (Allrod Rochow)
  • Heat of Fusion: 16.9 kJ/mol
  • Incompatibilities:
    Potassium nitrate, oxidizers
  • Ionization Potential
    • First: 6.84
    • Second: 13.13
    • Third: 22.99
  • Valence Electron Potential (-eV): 80

Physical Properties

  • Atomic Mass Average: 91.224
  • Boiling Point: 4650K, 4377C, 7911F
  • Coefficient of Lineal Thermal Expansion/K-1: 5.78E-6
  • Conductivity
    Electrical: 0.0236 106/cm
    Thermal: 0.227 W/cmK
  • Density: 6.51 g/cm3 @ 300K
  • Description:
    A hard rare grayish-white metal, which is resistant towards corrosion due to an oxide film on its surface. It will burn in air if ignited.
  • Elastic Modulus:
    • Bulk: 89.8/GPa
    • Rigidity: 35/GPa
    • Youngs: 98/GPa
  • Enthalpy of Atomization: 598 kJ/mole @ 25C
  • Enthalpy of Fusion: 20.9 kJ/mole
  • Enthalpy of Vaporization: 581.6 kJ/mole
  • Flammablity Class: Combustible
  • Freezing Point: see melting point
  • Hardness Scale
    • Brinell: 650 MN m-2
    • Mohs: 5
    • Vickers: 903 MN m-2
  • Heat of Vaporization: 58.2 kJ/mol
  • Melting Point: 2125K, 1852C, 3366F
  • Molar Volume: 14.06 cm3/mole
  • Physical State (at 20C & 1atm): Solid
  • Specific Heat: 0.27 J/gK
  • Vapor Pressure: 0.00168 Pa @ 1852C

Regulatory / Health

  • CAS Number
    • 7440-67-7 powder, wet
  • UN/NAID and ERG Guide Number
    • 1358  / 179 powder, wet
    • 1932  / 135 scrap
    • 2008  / 135 powder, dry
  • RTECS: ZH7070000
  • OSHA Permissible Exposure Limit (PEL)
    • TWA: 5 mg/m3
  • OSHA PEL Vacated 1989
    • TWA: 5 mg/m3
    • STEL: 10 mg/m3
  • NIOSH Recommended Exposure Limit (REL)
    • TWA: 5 mg/m3
    • STEL: 10 mg/m3
    • IDLH: 50 mg/m3
  • Routes of Exposure: Inhalation; Skin and/or eye contact
  • Target Organs: Skin, respiratory system
  • Levels In Humans:
    Note: this data represents naturally occuring levels of elements in the typical human, it DOES NOT represent recommended daily allowances.
    • Blood/mg dm-3: 0.011
    • Bone/p.p.m: <0.1
    • Liver/p.p.m: 0.11
    • Muscle/p.p.m: 0.08
    • Daily Dietary Intake: 0.05 mg
    • Total Mass In Avg. 70kg human: 1 mg

Who / Where / When / How

  • Discoverer: Martin H. Klaproth
  • Discovery Location: Berlin Germany
  • Discovery Year: 1789
  • Name Origin:
    Arabic, zargun for gold color.
  • Abundance:
    • Earth's Crust/p.p.m.: 190
    • Seawater/p.p.m.: 0.000009
    • Atmosphere/p.p.m.: N/A
    • Sun (Relative to H=1E12): 560
  • Sources:
    Found in many minerals such as zircon and baddeleyite. Annual world wide production is around 7000 tons. Primary mining areas are Australia, Brazil, USA and Sri Lanka.
  • Uses:
    Used in alloys such as zircaloy which is used in nuclear applications since it does not readily absorb neutrons. Also used in catalytic converters, percussion caps and furnace bricks. Baddeleyite is used in lab crucibles.
  • Additional Notes:
    While Klaproth discovered zirconium in 1789, it first isolated by J.J. Berzelius in 1824 in stockholm Sweden.

Ionization Energy (eV): 6.634 eV
Estimated Crustal Abundance: 1.65102 milligrams per kilogram
Estimated Oceanic Abundance:
310-5 milligrams per liter

Transition Metals
Group 3
(IIIB)
4
(IVB)
5
(VB)
6
(VIB)
7
(VIIB)
8
(VIIIB)
9
(VIIIB)
10 (VIIIB) 11
(IB)
12
(IIB)
Period 4 21
Sc
44.95
22
Ti
47.86
23
V
50.94
24
Cr
51.99
25
Mn
54.93
26
Fe
55.84
27
Co
58.93
28
Ni
58.69
29
Cu
63.54
30
Zn
65.39
Period 5 39
Y
88.90
40
Zr
91.22
41
Nb
92.90
42
Mo
95.94
43
Tc
98.00
44
Ru
101.0
45
Rh
102.9
46
Pd
106.4
47
Ag
107.8
48
Cd
112.4
Period 6 57
La
138.9
72
Hf
178.4
73
Ta
180.9
74
W
183.8
75
Re
186.2
76
Os
190.2
77
Ir
192.2
78
Pt
195.0
79
Au
196.9
80
Hg
200.5
Period 7 89
Ac
227.0
104
Rf
261.0
105
Db
262.0
106
Sg
266.0
107
Bh
264.0
108
Hs
269.0
109
Mt
268.0
110
Ds
269.0
111
Rg
272.0
112
Uub
277.0