Editing Period 6 element (section)

===Hafnium===
{{main|Hafnium}}
'''Hafnium''' is a [[chemical element]] with the [[element symbol|symbol]] '''Hf''' and [[atomic number]] 72. A [[lustre (mineralogy)|lustrous]], silvery gray, [[tetravalence|tetravalent]] [[transition metal]], hafnium chemically resembles [[zirconium]] and is found in zirconium [[mineral]]s. Its existence was [[Mendeleev's predicted elements|predicted by Dmitri Mendeleev]] in 1869. Hafnium was the penultimate [[stable isotope]] element to be discovered ([[rhenium]] was identified two years later). Hafnium is named for ''Hafnia'', the [[Latin]] name for "[[Copenhagen]]", where it was discovered.

Hafnium is used in filaments and electrodes.  Some [[semiconductor]] fabrication processes use its oxide for [[integrated circuits]] at 45&nbsp;nm and smaller feature lengths. Some [[superalloy]]s used for special applications contain hafnium in combination with [[niobium]], [[titanium]], or [[tungsten]].

Hafnium's large [[neutron capture]] cross-section makes it a good material for [[neutron]] absorption in [[control rod]]s in [[nuclear power plant]]s, but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors.