пятница, 8 ноября 2019 г.

Hafnium Facts (Atomic Number 72 or Hf)

Hafnium Facts (Atomic Number 72 or Hf) Hafnium is an element that was predicted by Mendeleev (of periodic table fame) before it was actually discovered. Here is a collection of fun and interesting facts about hafnium, as well as standard atomic data for the element: Hafnium Element Facts Fresh, pure hafnium is a metal with a bright, silvery luster. However, hafnium oxidizes to form a beautiful rainbow colored surface effect.Mendeleev predicted the existence of hafnium in a report he prepared in 1869. It was one of two non-radioactive elements believed to exist, but not verified. It was finally discovered in 1923 by Georg von Hevesy and Dirk Coster by using x-ray spectroscopy on a zirconium ore sample. The element name honors the city of its discovery (Hafnia is the old name for Copenhagen).As you might expect, hafnium is not found free in nature. Instead, it forms compounds and alloys. Because the two metals share similar occurrence and properties, hafnium is extremely difficult to separate from zirconium. Most hafnium metal has some degree of zirconium contamination. Although hafnium is found with ores (mainly zircon and baddeleyite), it is not as reactive as most transition metals.When hafnium is powdered, the increased surface area improves its reactivity. Powdere d hafnium readily ignites and may explode. Hafnium finds use as an alloying agent for iron, titanium, niobium, and tantalum. It is found in integrated circuits, vacuum tubes, and incandescent lamps. Hafnium is used in nuclear reactors, mainly as nuclear control rods because hafnium is an exceptionally powerful neutron absorber. This is one significant difference between hafnium and its sister element zirconium zirconium is essentially transparent to neutrons.Hafnium in its pure form is not particularly toxic, but it does represent a health hazard, particularly if inhaled. Hafnium compounds should be handled with care, as should any transition metal compound, because the ionic forms be dangerous. Only limited testing has been done on the effect of hafnium compounds in animals. All that is really known is that hafnium usually exhibits a valence of 4.Hafnium is found in the gemstones zircon and garnet. Hafnium in garnet may be used as a geochronometer, which means it can be used to date metamorphic geological events. Hafnium Atomic Data Element Name: Hafnium Hafnium Symbol: Hf Atomic Number: 72 Atomic Weight: 178.49 Element Classification: Transition Metal Electron Configuration: [Xe] 4f14 5d2 6s2 Discovery: Dirk Coster and Georg von Hevesy 1923 (Denmark) Name Origin: Hafnia, the Latin name of Copenhagen. Density (g/cc): 13.31 Melting Point (K): 2503 Boiling Point (K): 5470 Appearance: silvery, ductile metal Atomic Radius (pm): 167 Atomic Volume (cc/mol): 13.6 Covalent Radius (pm): 144 Ionic Radius: 78 (4e) Specific Heat (20Â °C J/g mol): 0.146 Fusion Heat (kJ/mol): (25.1) Evaporation Heat (kJ/mol): 575 Pauling Negativity Number: 1.3 First Ionizing Energy (kJ/mol): 575.2 Oxidation States: 4 Lattice Structure: hexagonal Lattice Constant (Ã…): 3.200 Lattice C/A Ratio: 1.582 Hafnium Fast Fasts Element Name: HafniumElement Symbol: HfAtomic Number: 72Appearance: Steel gray metalGroup: Group 4 (Transition Metal)Period: Period 6Discovery:Â  Dirk Coster and George de Hevesy (1922) Sources Hevesy, G. (1925). The Discovery and Properties of Hafnium. Chemical Reviews. 2: 1–41. doi:10.1021/cr60005a001Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 971–975. ISBN 0-08-037941-9.Lee, O. Ivan (1928). The Mineralogy of Hafnium. Chemical Reviews. 5: 17–37. doi:10.1021/cr60017a002Schemel, J. H. (1977). ASTM Manual on Zirconium and Hafnium. ASTM International. pp. 1–5. ISBN 978-0-8031-0505-8.Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.

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