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Hafnium (Hf)

QUICK REFERENCE

  • Symbol: Hf
  • Atomic Number: 72
  • Atomic Weight: 178.49
  • Element Classification: Transition Metal
  • Discovered By: Dirk Coster and George Charles de Hevesy
  • Discovery Date: 1923
  • Name Origin: Named after Hafnia, the Latin name for Copenhagen
  • Density(g/cc): 13.31
  • Melting Point: 2233°C
  • Boiling Point: 4603°C
  • Appearance: Silvery gray, ductile metal
  • Atomic Radius(pm): 159

Discovery

Hafnium was discovered in 1923 by Dutch physicist Dirk Coster and Hungarian chemist George Charles de Hevesy. The discovery occurred in Copenhagen, Denmark, through X-ray spectroscopy analysis of zirconium ore. Hafnium was the last stable element to be discovered, filling a predicted gap in the periodic table. It was named after Hafnia, the Latin name for Copenhagen, in honor of the city where it was identified.

Relation to Other Elements

Hafnium is a transition metal, closely related to zirconium, with which it shares nearly identical chemical and physical properties due to the lanthanide contraction. This similarity makes the separation of hafnium from zirconium challenging. Hafnium is unique among transition metals for its high affinity for oxygen, forming stable oxides. It exhibits a +4 oxidation state in most of its compounds.

Natural Occurrence

Hafnium is not found free in nature but is found in most zirconium minerals, including zircon (ZrSiO₄) and baddeleyite (ZrO₂). It is relatively rare, comprising about 0.00058% of the Earth’s crust by weight. The principal mining areas for hafnium-bearing minerals are in Australia, South Africa, and the United States.

Uses

Hafnium has several important applications, leveraging its ability to absorb neutrons and its high-temperature stability:

  • Nuclear Reactors: Hafnium is used in control rods for nuclear reactors due to its high capacity for absorbing neutrons, helping to regulate the nuclear fission process.
  • Alloys: Hafnium is added to nickel-based superalloys to improve their mechanical properties and thermal stability, making them suitable for turbine blades in jet engines and gas turbines.
  • Semiconductor Industry: Hafnium-based compounds are used in the production of semiconductor devices, including integrated circuits and processors, as a gate insulator to replace silicon dioxide, enhancing the performance of the devices.
  • Filament and Electrodes: Hafnium is used in plasma cutting torches and welding electrodes because of its ability to emit electrons when heated.

The discovery of hafnium and its subsequent integration into key industrial and technological applications highlight the element’s importance in modern science and engineering. Its role in enhancing the safety and efficiency of nuclear reactors and improving the performance of electronic devices underscores the value of hafnium in advancing technological capabilities.

Lutetium (Lu)

Tantalum (Ta)