Hafnium ( Hf )
The existence of hafnium was predicted many years before it was first identified in zircon from Norway, by means of X-ray spectroscopic analysis in 1923 by Coster and von Hevesey.
Hafnium was expected to be associated with zirconium. Most zirconium minerals contain 1 to 5% hafnium.
Hafnium and zirconium are two of the most difficult elements to separate. Their chemistries are almost identical, except for there densities where hafnium is double that of zirconium.
Hafnium is resistant to concentrated alkalis, but will react with oxygen, nitrogen, carbon, boron, sulphur and silicon, with halogens directly reacting to form tetrahalides at elevated temperatures.