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Hf - Hafnium

Hafnium

 Hafnium 
Hf
Atomic Number: 72
Atomic Weight: 178.49
Element Type: Transition Metal
Crystal Structure: Hexagonal
Melting Point: 2233.0°C = 4051.4°F = 2506.15 K
Boiling Point: 4603.0°C = 8317.4°F = 4876.15 K
Critical Temp: °C = °F = K
Atomic Radius: 2.16 Å (Å = Angstrom = 10-10 m)
Covalent Radius: 1.44 Å
Electronegativity: 1.3

History

(Hafinia, Latin name for Copenhagen) Many years before its discovery in 1932 (creditedto D. Coster and G. von Hevesey), Hafnium was thought to be present in various mineralsand concentrations. On the basis of the Bohr theory, the new element was expected to beassociated with zirconium.

It was finally identified in zircon from Norway, by means of X-ray spectroscopeanalysis. It was named in honor of the city in which the discovery was made. Mostzirconium minerals contain 1 to 5 percent hafnium.

It was originally separated from zirconium by repeated recrystallization of the doubleammonium or potassium fluorides by von Hevesey and Jantzen. Metallic hafnium was firstprepared by van Arkel and deBoer by passing the vapor of the tetraiodide over a heatedtungsten filament. Almost all hafnium metal now produced is made by reducing thetetrachloride with magnesium or with sodium (Kroll Process).


Sources


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