HAFNIUM
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HAFNIUM |
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Introduction |
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| Atomic Number: | 72 | Group: | 4 or IV B | 72 | 178.49 |
| Average Atomic Mass: | 178.49 | Period: | 6 |
Hf |
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CAS Number: |
7440-58-6 | ||||
| Hafnium | |||||
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Classification |
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| Metal | Nonmetal | Metalloid | ||
| Alkali Metal | Alkali Earth Metal | Transition Metal | Chalcogen | Halogen |
| Noble Gas | Lanthanoid | Actinoid |
Rare Earth Metal |
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| Transuranium | No Stable Isotopes | |||
| Solid | Liquid | Gas |
Assumed Solid |
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Description |
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| Hafnium was thought to be present in various minerals and concentrations many years prior to its discovery, in 1923, credited to D. Coster and G. von Hevesey. On the basis of the Bohr theory, the new element was expected to be associated with zirconium. It was finally identified in zircon from Norway, by means of X-ray spectroscopic analysis. It was named in honor of the city in which the discovery was made. Most zirconium minerals contain 1 to 5% hafnium. It was originally separated from zirconium by repeated recrystallization of the double ammonium or potassium fluorides by von Hevesey and Jantzen. Metallic hafnium was first prepared by van Arkel and deBoer by passing the vapor of the tetraiodide over a heated tungsten filament. Almost all hafnium metal now produced is made by reducing the tetrachloride with magnesium or with sodium (Kroll Process). Hafnium is a ductile metal with a brilliant silver luster. Its properties are considerably influenced by the impurities of zirconium present. Of all the elements, zirconium and hafnium are two of the most difficult to separate. Their chemistry is almost identical, however, the density of zirconium is about half that of hafnium. Very pure hafnium has been produced, with zirconium being the major impurity. Natural hafnium contains six isotopes, one of which is slightly radioactive. Hafnium has a total of 40 recognized isotopes and isomers. Because hafnium has a good absorption cross section for thermal neutrons (almost 600 times that of zirconium), has excellent mechanical properties, and is extremely corrosion resistant, it is used for reactor control rods. Such rods are used in nuclear submarines. Hafnium has been successfully alloyed with iron, titanium, niobium, tantalum, and other metals. Hafnium carbide is the most refractory binary composition known, and the nitride is the most refractory of all known metal nitrides (m.p. 3310°C). Hafnium is used in gas-filled and incandescent lamps, and is an efficient “getter” for scavenging oxygen and nitrogen. Finely divided hafnium is pyrophoric and can ignite spontaneously in air. Care should be taken when machining the metal or when handling hot sponge hafnium. At 700°C hafnium rapidly absorbs hydrogen to form the composition HfH1.86. Hafnium is resistant to concentrated alkalis, but at elevated temperatures reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. Halogens react directly to form tetrahalides. The price of the metal is in the broad range of $1/g to $3/g, depending on purity and quantity. The yearly demand for hafnium in the U.S. is now in excess of 50,000 kg. 1 |
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Physical Properties |
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| Normal Melting Point: | 2233 °C = 2506.15 K = 4051.4 °F 2 | Normal Boiling Point: | 4603 °C = 4876.15 K = 8317.4 °F 2 |
| Sublimation Point: | Triple Point: | ||
| Critical Point: | |||
| Density: | 13.3 g/cm3 | Crystal Structure: | hexagonal |
| Atomic Radius: | 2.16 Ǻ = 216 pm | Covalent Radius: | 1.44 Ǻ = 144 pm |
| Ionic Radius: | 1 Ǻ = 100 pm | Atomic Volume: | 13.6 cm3/mol |
| Qualitative Solubility: | s HF 3 | ||
| Note: Unless otherwise stated, solubility is for water at 25 degrees Celsius. | |||
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Electron Configuration and Bonding |
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| Predicted Electron Configuration: | [Xe] 6s2 4f14 5d2 |
Lewis Dot Diagram |
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| Actual Electron Configuration: | [Xe] 6s2 4f14 5d2 |
x |
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| Block: | d | Hf |
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| Highest Occupied Energy Level: | 6 | |||||||
| Valence Electrons: | 2 | |||||||
| Quantum Numbers: | n = 5 | ℓ = 2 | mℓ = -1 | ms = +½ | ||||
| Please note that information in this section can be derived entirely from the periodic table. Although most people do not discuss valence electrons of the d-block and f-block elements, on this page the number of electrons in the highest energy level of the actual electron configuration was used to determine valence electrons. | ||||||||
| Electronegativity (Pauling): | 1.3 | Electropositivity (Pauling): | 2.7 | ||||
| Electron Affinity: | 0.00 eV = 0.00 kJ/mol = 0.00 kcal/mol | Oxidation States: | +4 | ||||
| Ionization Potential 4 | eV | kJ/mol | Ionization Potential 4 | eV | kJ/mol | ||
| 1 | 6.82507 | 658.5 | 3 | 23.3 | 2248.1 | ||
| 2 | 14.9 | 1437.6 | 4 | 33.33 | 3215.9 | ||
| Note: Only the electronvolt values are given in the CRC Handbook, a conversion factor was used to find the kJ/mol value. | |||||||
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Thermochemistry |
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| Specific Heat: | 0.14 J/g°C = 0.033 cal/g°C | Thermal Conductivity: | 23 (W/m)/K, 27ºC | ||||
| Heat of Fusion: | 24.06 kJ/mol = 134.8 J/g | Heat of Vaporization: | 575 kJ/mol = 3221.5 J/g | ||||
| State of Matter | Enthalpy of Formation | Entropy of Formation | Gibbs Free Energy | ||||
| (kcal/mol) | (kJ/mol) | (cal/K) | (J/K) | (kcal/mol) | (kJ/mol) | ||
| (s hexagonal) | 0 | 0 | 10.41 | 43.55544 | 0 | 0 | |
| (g) | 148.0 | 619.232 | 44.642 | 186.782128 | 137.8 | 576.5552 | |
| (g) | -64.80 | -271.1232 | 41.51 | 173.67784 | -65.30 | -273.2152 | |
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Video |
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| Video on hafnium from the University of Nottingham's periodicvideos.com |
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Isotopes |
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| Nuclide | Mass | Half-Life | Nuclear Spin | Binding Energy (kJ/mol) |
| 153Hf | 152.97069(54)# | 400# ms [>200 ns] | 1/2+# | 114152202289.275 |
| 154Hf | 153.96486(54)# | 2(1) s | 0+ | 115830425606.564 |
| 155Hf | 154.96339(43)# | 890(120) ms | 7/2-# | 116609836551.828 |
| 156Hf | 155.95936(22) | 23(1) ms | 0+ | 118288059869.119 |
| 157Hf | 156.95840(21)# | 115(1) ms | 7/2- | 119067470814.387 |
| 158Hf | 157.954799(19) | 2.84(7) s | 0+ | 119846881759.654 |
| 159Hf | 158.953995(18) | 5.20(10) s | 7/2-# | 120626292704.923 |
| 160Hf | 159.950684(12) | 13.6(2) s | 0+ | 121405703650.189 |
| 161Hf | 160.950275(24) | 18.2(5) s | 3/2-# | 122185114595.455 |
| 162Hf | 161.94721(1) | 39.4(9) s | 0+ | 123863337912.741 |
| 163Hf | 162.94709(3) | 40.0(6) s | 3/2-# | 124642748858.01 |
| 164Hf | 163.944367(22) | 111(8) s | 0+ | 125422159803.279 |
| 165Hf | 164.94457(3) | 76(4) s | (5/2-) | 126201570748.543 |
| 166Hf | 165.94218(3) | 6.77(30) min | 0+ | 126980981693.812 |
| 167Hf | 166.94260(3) | 2.05(5) min | (5/2)- | 127760392639.081 |
| 168Hf | 167.94057(3) | 25.95(20) min | 0+ | 128539803584.347 |
| 169Hf | 168.94126(3) | 3.24(4) min | (5/2)- | 129319214529.613 |
| 170Hf | 169.93961(3) | 16.01(13) h | 0+ | 130997437846.904 |
| 171Hf | 170.94049(3) | 12.1(4) h | 7/2(+) | 130878036420.149 |
| 172Hf | 171.939448(26) | 1.87(3) a | 0+ | 132556259737.434 |
| 173Hf | 172.94051(3) | 23.6(1) h | 1/2- | 132436858310.684 |
| 174Hf | 173.940046(3) | 2.0(4)E+15 a | 0+ | 133216269255.95 |
| 175Hf | 174.941509(3) | 70(2) d | 5/2- | 133995680201.216 |
| 176Hf | 175.9414086(24) | STABLE | 0+ | 134775091146.485 |
| 177Hf | 176.9432207(23) | STABLE | 7/2- | 135554502091.752 |
| 178Hf | 177.9436988(23) | STABLE | 0+ | 136333913037.018 |
| 179Hf | 178.9458161(23) | STABLE | 9/2+ | 137113323982.287 |
| 180Hf | 179.9465500(23) | STABLE | 0+ | 137892734927.553 |
| 181Hf | 180.9491012(23) | 42.39(6) d | 1/2- | 138672145872.82 |
| 182Hf | 181.950554(7) | 8.90(9)E+6 a | 0+ | 138552744446.066 |
| 183Hf | 182.95353(3) | 1.067(17) h | (3/2-) | 139332155391.335 |
| 184Hf | 183.95545(4) | 4.12(5) h | 0+ | 140111566336.602 |
| 185Hf | 184.95882(21)# | 3.5(6) min | 3/2-# | 140890977281.868 |
| 186Hf | 185.96089(32)# | 2.6(12) min | 0+ | 140771575855.112 |
| 187Hf | 186.96459(43)# | 30# s [>300 ns] | 141550986800.381 | |
| 188Hf | 187.96685(54)# | 20# s [>300 ns] | 0+ | 142330397745.647 |
| Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 5 | ||||
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Reactions |
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Abundance |
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| Earth: | Source Compounds: | oxides 6 |
| Earth: | Ocean Water: | 0.000007 mg/L 7 |
| Earth: | Crust: | 3 mg/kg = 0.0003% 7 |
| Earth: | Total: | 230 ppb 8 |
| Mercury: | Total: | 177 ppb 8 |
| Venus: | Total: | 241 ppb 8 |
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Compounds |
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Safety |
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| Note: Not every link below has an entry for every element on the periodic table. Sites were selected based on those that had a large number of element and compound entries. |
| Scorecard's Pollution Information − not an MSDS, but it does provide basic information (among other things) on human heath hazards and industrial uses. |
| Although not truly an MSDS, Oxford University's Physical and Theoretical Chemistry Laboratory does provide some basic information. |
| Iowa State University |
| ESPI Metals |
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Languages |
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| Afrikaans: | Hafnium | Albanian: | Hafnium | Armenian: | Հաֆնիում | Arabic: | هافنيوم |
| Aromanian: | Hafniumu | Basque: | Hafnioa | Bosnian: | Hafnij | Breton: | Hafniom |
| Bulgarian: | Хафиий | Byelorussian: | Гафній | Catalan: | Hafni | Chinese: | 铪 |
| Cornish: | Hafnyum | Croatian: | Hafnij | Czech: | Hafnium | Danish: | Hafnium |
| Dutch: | Hafnium | Esperanto: | Hafnio | Estonian: | Hafnium | Faroese: | Hafnium |
| Finnish: | Hafnium | French: | Hafnium | Friulian: | Afni | Frisian: | Hafnium |
| Galician: | Hafnio | Georgian: | ჰაფნიუმი | German: | Hafnium | Greek: | Άφνιο |
| Hebrew: | הפניום | Hungarian: | Hafnium | Icelandic: | Hafnín | Irish Gaelic: | Haifniam |
| Italian: | Hafnio | Japanese: | ハフニウム | Kashubian: | Hafen | Kazakh: | Гафний |
| Korean: | 하프늄 | Latvian: | Hafnijs | Lithuanian: | Hafnis | Luxembourgish: | Hafnium |
| Macedonian: | Хафниум | Malay: | Hafnium | Maltese: | Hafnjum | Manx Gaelic: | Hafnium |
| Mokshan: | Гафни | Mongolian: | Гафни | Norwegian: | Hafnium | Occitan: | Afni |
| Ossetian: | Гафний | Polish: | Hafn | Portuguese: | Háfnio | Russian: | Гафний |
| Scottish Gaelic: | Haifniam | Serbian: | Хафниjум | Slovak: | Hafnium | Spanish: | Hafnio |
| Sudovian: | Hafnijan | Swahili: | Hafni | Swedish: | Hafnium | Tajik: | Gafni' |
| Thai: | แฮฟเนียม | Turkish: | Hafniyum | Ukranian: | Гафній | Uzbek: | Гафний |
| Vietnamese: | Hafini | Welsh: | Haffniwm |
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For More Information |
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Sources |
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| (1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4-14. |
| (2) - Lide, David R. CRC Handbook; CRC Press: Boca Raton, FL, 2002; p 4-132. |
| (3) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4-8 - 4-149. |
| (4) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10-178 - 10-180. |
| (5) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009). |
| (6) - Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change, 4th ed.; McGraw-Hill Higher Education: Boston, MA, 2006, p 965. |
| (7) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14-17. |
| (8) - Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change, 4th ed.; McGraw-Hill Higher Education: Boston, MA, 2006, p 962. |
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HAFNIUM |
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| Site designed and maintained by Mr. Everett. |
| Last update: Thursday, August 12, 2010 |