Hafnium (Hf)

General Information

• Symbol: Hf
• Atomic Number: 72
• Atomic Weight: 178.49 u
• Element Category: Transition metal
• Group: 4
• Period: 6
• Block: d-block

Physical Properties

• Appearance: Silvery-gray metallic
• Density: 13.31 g/cm³
• Melting Point: 2233 °C (4051 °F)
• Boiling Point: 4603 °C (8317 °F)
• Phase at STP: Solid
• Electron Configuration: [Xe] 4f¹⁴ 5d² 6s²
• Oxidation States: +4 (most common)

Chemical Properties

• Reactivity: Resistant to corrosion due to the formation of a protective oxide film on its surface; reacts with halogens and acids.
• Compounds: Forms compounds such as hafnium dioxide (HfO₂), hafnium tetrachloride (HfCl₄), and hafnium carbide (HfC).

Uses and Applications

• Nuclear Reactors: Used in control rods due to its ability to absorb neutrons without forming long-lived radioactive isotopes.
• Alloys: Added to high-temperature alloys used in aerospace and industrial applications for its high melting point and corrosion resistance.
• Electronics: Utilized in the production of semiconductors and integrated circuits, particularly in gate insulators.
• Ceramics: Used in the manufacture of high-performance ceramics and refractory materials.
• Optics: Employed in optical coatings and as a getter in vacuum tubes.

Occurrence and Extraction

• Natural Occurrence: Found in minerals such as zircon (ZrSiO₄) and baddeleyite (ZrO₂), often in conjunction with zirconium.
• Extraction: Extracted as a byproduct of zirconium refining through processes like solvent extraction and reduction with magnesium or sodium.

Isotopes

• Stable Isotopes: Hafnium has six stable isotopes: Hafnium-174, Hafnium-176, Hafnium-177, Hafnium-178, Hafnium-179, and Hafnium-180.
• Radioactive Isotopes: Several radioactive isotopes, including Hafnium-182, used in scientific research.

Safety and Handling

• Hazards: Generally considered to be of low toxicity; however, hafnium powder can be a fire hazard and should be handled with care.
• Precautions: Store hafnium powder in a cool, dry place away from sources of ignition and handle with appropriate protective equipment.

History

• Discovery: Discovered by Dirk Coster and George de Hevesy in 1923.
• Name Origin: Named after “Hafnia,” the Latin name for Copenhagen, where it was discovered.

Additional Facts

• Crystal Structure: Hexagonal close-packed (hcp)
• Magnetic Properties: Paramagnetic
• Thermal Conductivity: Moderate, about 23 W/m·K
• Electrical Resistivity: About 331 nΩ·m at room temperature

Summary

Hafnium is a transition metal known for its high melting point, corrosion resistance, and significant applications in nuclear reactors, high-temperature alloys, electronics, ceramics, and optics. It is found in minerals like zircon and extracted as a byproduct of zirconium refining. Despite its low toxicity, hafnium powder should be handled carefully due to its potential fire hazard.

40 Question and Answer Pairs About Hafnium

1. What is the atomic number of Hafnium?

   • 72

2. What is the symbol for Hafnium?

   • Hf

3. What is the atomic weight of Hafnium?

   • 178.49 u

4. In which group of the periodic table is Hafnium found?

   • Group 4

5. What period is Hafnium in?

   • Period 6

6. What block does Hafnium belong to?

   • d-block

7. What is the melting point of Hafnium?

   • 2233 °C (4051 °F)

8. What is the boiling point of Hafnium?

   • 4603 °C (8317 °F)

9. What is the density of Hafnium?

   • 13.31 g/cm³

10. What is the electron configuration of Hafnium?

    • [Xe] 4f¹⁴ 5d² 6s²

11. What is the common oxidation state of Hafnium?

    • +4

12. What is the appearance of Hafnium?

    • Silvery-gray metallic

13. Is Hafnium reactive with air?

    • No, it forms a protective oxide layer that resists corrosion.

14. Name a compound of Hafnium.

    • Hafnium dioxide (HfO₂)

15. What is a common use of Hafnium in nuclear reactors?

    • Used in control rods to absorb neutrons.

16. How is Hafnium used in aerospace?

    • Added to high-temperature alloys for improved performance.

17. What role does Hafnium play in electronics?

    • Used in the production of semiconductors and integrated circuits.

18. How is Hafnium used in ceramics?

    • In high-performance ceramics and refractory materials.

19. What application does Hafnium have in optics?

    • Used in optical coatings and as a getter in vacuum tubes.

20. Name a mineral that contains Hafnium.

    • Zircon (ZrSiO₄)

21. How is Hafnium extracted from ores?

    • As a byproduct of zirconium refining through solvent extraction.

22. What is the most stable isotope of Hafnium?

    • Hafnium-180

23. Name a radioactive isotope of Hafnium used in research.

    • Hafnium-182

24. What safety hazard is associated with Hafnium powder?

    • It can be a fire hazard.

25. Who discovered Hafnium?

    • Dirk Coster and George de Hevesy

26. Where does the name Hafnium come from?

    • From “Hafnia,” the Latin name for Copenhagen.

27. What is the crystal structure of Hafnium?

    • Hexagonal close-packed (hcp)

28. Is Hafnium paramagnetic or diamagnetic?

    • Paramagnetic

29. What is the thermal conductivity of Hafnium?

    • About 23 W/m·K

30. What is the electrical resistivity of Hafnium at room temperature?

    • About 331 nΩ·m

31. What is the primary oxidation state of Hafnium?

    • +4

32. Is Hafnium found as a free element in nature?

    • No, it is found in minerals like zircon.

33. What is the common name of hafnium tetrachloride?

    • HfCl₄

34. What is a major application of hafnium carbide (HfC)?

    • Used in high-temperature ceramics.

35. How does Hafnium benefit nuclear reactors?

    • By absorbing neutrons without forming long-lived radioactive isotopes.

36. What is the boiling point of Hafnium in Kelvin?

    • 4876 K

37. What group does Hafnium belong to in the periodic table?

    • Transition metals

38. What is the natural abundance of Hafnium-180?

    • About 35%

39. Can Hafnium be used in high-temperature applications?

    • Yes, due to its high melting and boiling points.

40. What is the key property that makes Hafnium valuable in electronics?

    • Its use in gate insulators for semiconductors.