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Hafnium Facts & Worksheets

Hafnium is a chemical element with the symbol Hf and atomic number 72. Hafnium is a glossy, silvery gray tetravalent transition metal that chemically mimics zirconium and can be found in many zirconium minerals.

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Hafnium is a chemical element with the symbol Hf and atomic number 72. Hafnium is a glossy, silvery gray tetravalent transition metal that chemically mimics zirconium and can be found in many zirconium minerals.

See the fact file below for more information about Hafnium, or you can download our 28-page Hafnium worksheet pack to utilize within the classroom or home environment.

Key Facts & Information

HISTORICAL BACKGROUND

  • Dmitri Mendeleev predicted its existence in 1869, but it was not detected until 1922 by Dirk Coster and George de Hevesy, which made it one of the last two solid substances discovered. Masataka Ogawa discovered the element rhenium in 1908. Still, its atomic number was misdiagnosed at the time, and the field of science did not widely recognize it until it was discovered again by Walter Noddack, Ida Noddack, and Otto Berg in 1925.
  • This makes it impossible to establish whether hafnium or rhenium was discovered first. Meanwhile, hafnium is named after Hafnia, the Latin word for Copenhagen, where it was found.
  • Hafnium is used in electrodes and filaments. Its oxide is used in several semiconductor production techniques for 45-nanometer integrated circuits and shorter feature lengths. Hafnium can be found in several superalloys combined with niobium, titanium, or tungsten for unique purposes.
  • Hafnium’s large neutron-capturing cross section makes it an ideal material for neutron absorption in nuclear power plant control rods. Still, it must also be removed from the neutron-transparent, corrosion-resistant zirconium alloys used by nuclear reactors.

CHARACTERISTICS

  • Physical Characteristics. Hafnium is a bright, silvery, ductile metal resistant to corrosion. It is chemically related to zirconium in that it has the same valence electrons and belongs to the same group.
  • The lanthanide contraction completely cancels the projected atomic radius expansion from periods 5 to 6. At 2388 K, hafnium transitions from the alpha form, a hexagonal close-packed lattice, to the beta form, a body-centered cubic lattice.
  • The two most remarkable nuclear characteristics of hafnium are its sizeable thermal neutron absorption and the ease with which the nuclei of various hafnium isotopes can quickly absorb two or more neutrons.
  • Chemical Characteristics. When hafnium is exposed to air, it interacts to create a barrier that stops more corrosion. Despite this, the metal is susceptible to oxidation by halogens or air burning and attacked by hydrofluoric acid and strong sulfuric acid. Finely divided hafnium can spontaneously fire in the air like its sister metal, zirconium.
  • The chemistry of zirconium and hafnium is sufficiently similar due to lanthanide contraction, so the two cannot be distinguished using different chemical processes. The main chemical differences between these two elements are their melting and boiling temperatures and solubility in solvents.
  • Isotopes. There are at least 40 known hafnium isotopes, with mass numbers ranging from 153 to 192. The mass numbers of the five stable isotopes range from 176 to 180. The half-lives of the radioactive isotopes range from 400 ms to 153Hf, which is the most stable.
  • Occurrence. Hafnium is expected to account for 3.0 to 4.8 ppm of the Earth’s upper crust by mass. It is not a free element on Earth but in a solid form with zirconium in natural zirconium compounds like zircon (ZrSiO4).
  • Heavy mineral sands ore deposits, pegmatites, especially in Brazil and Malawi, and carbonatite breaches, notably the Crown Polymetallic Deposit at Mount Weld in Western Australia, are vital sources of zircon (and thus hafnium) ores. Trachyte tuffs in Dubbo, New South Wales, Australia, contain uncommon zircon-hafnium silicates eudialyte or armstrongite, which could be a source of hafnium.
  • Production. Zirconium is an excellent metal for cladding nuclear fuel rods due to its low neutron capture cross-section and chemical stability at high temperatures. Due to hafnium neutron-absorbing characteristics, hafnium impurities in zirconium would render it significantly less viable for nuclear reactor uses. 
  • The chemical characteristics of hafnium and zirconium are almost identical. The earliest procedures used were fractional crystallization of ammonium fluoride salts or inadequate for industrial-scale manufacturing.
  • The chemical characteristics of hafnium and zirconium are almost identical. The earliest procedures used were fractional crystallization of ammonium fluoride salts or inadequate for industrial-scale manufacturing.
  • Hafnium and zirconium naturally occur together, and their ionic radii are similar, making chemical separation difficult. Hafnium appears to form inorganic compounds in the +4 oxidation state. Halogens react with it, forming hafnium tetrahalides. At elevated temperatures, hafnium interacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. 

APPLICATION

  • Several factors contribute to hafnium’s limited technical applications: first, the close similarity between hafnium and zirconium allows the more abundant zirconium to be used for most applications.
  • Second, hafnium was first available as pure metal after using hafnium-free zirconium in the nuclear industry in the late 1950s. Furthermore, the limited quantity and the rigorous separation processes required make it a scarce commodity.
  • Nuclear reactors. The nuclei of certain hafnium isotopes can absorb multiple neutrons. This makes hafnium a suitable material for nuclear reactor control rods. Its excellent mechanical qualities and superior corrosion resistance make it appropriate for use in the demanding conditions of pressurized water reactors.
  • Alloys. Hafnium is used in alloys that include iron, titanium, niobium, tantalum, and other metals. Small amounts of hafnium improve the adhesion of protective oxide scales to nickel-based alloys. It also enhances corrosion resistance, particularly under cyclic temperature circumstances that tend to shatter oxide scales, by causing thermal tensions among the bulk material and the oxide layer.
  • Microprocessors. Hafnium-based compounds are used as insulators in transistor gates in Intel, IBM, and other integrated circuits with 45 nm (or less) process nodes. Hafnium oxide-based compounds are viable high-k dielectrics, allowing for a reduction in gate leakage current and, hence, improved performance at such scales.
  • Other uses. Along with its heat resilience and affinity for oxygen and nitrogen, hafnium is an adequate oxygen and nitrogen scavenger in gas-filled and incandescent lights. Hafnium is also employed as an electrode in plasma cutting due to its capacity to emit electrons into the air.

PRECAUTIONS

  • Hafnium is pyrophoric, meaning small particles can spontaneously fire when exposed to air; hence, machining requires caution. Most humans are infrequently exposed to compounds containing this element. Pure metal is not poisonous. However, hafnium compounds should be treated as toxic because ionic forms of metals are often the most harmful, and there has been limited animal testing on hafnium compounds.
  • People can be exposed to hafnium in the workplace through breathing, swallowing, skin touch, or eye contact. The National Institute for Occupational Safety and Health (NIOSH) has established the same recommended exposure limit (REL). At 50 mg/m3, hafnium poses an immediate threat to life and health.

Hafnium Worksheets

This fantastic bundle includes everything you need to know about Hafnium across 28 in-depth pages. These ready-to-use worksheets are perfect for teaching kids about Hafnium. Hafnium is a glossy, silvery gray tetravalent transition metal that chemically mimics zirconium and can be found in many zirconium minerals.

Complete List of Included Worksheets

Below is a list of all the worksheets included in this document.

  1. Hafnium Facts
  2. Hafnium Compounds
  3. Among Us
  4. AHA!-mazing Facts
  5. Complete the Table
  6. It Matters!
  7. Beginning of the History
  8. Between the Two
  9. #CaseSolved
  10. How About You?
  11. Hafnium Mysteries

Frequently Asked Questions

What is hafnium and where is it found in nature?

Hafnium is a chemical element with the symbol Hf and atomic number 72. It is a lustrous, silvery-gray transition metal that is chemically similar to zirconium. Hafnium is not found as a free element in nature but is typically found in minerals such as zircon (ZrSiO₄) and baddeleyite (ZrO₂), often in combination with zirconium. These minerals are extracted primarily in Australia, South Africa, and the United States.

What are the primary uses of hafnium?

Hafnium is used in several high-tech applications due to its unique properties. It is used in control rods for nuclear reactors because of its ability to absorb neutrons without forming long-lived radioactive isotopes. Hafnium is also used in aerospace applications, such as in rocket nozzles and spacecraft due to its high melting point and resistance to corrosion. Additionally, hafnium is used in the production of superalloys for jet engines and in the semiconductor industry for its role in the manufacture of integrated circuits.

What are the key properties of hafnium that make it suitable for its applications?

Hafnium has several key properties that make it suitable for its applications:

  • High melting point: Hafnium has a melting point of about 2233°C (4051°F), making it suitable for high-temperature applications.
  • Neutron absorption: It has excellent neutron absorption properties, which is crucial for its use in nuclear reactors.
  • Corrosion resistance: Hafnium is highly resistant to corrosion, particularly in acidic environments.
  • Mechanical strength: It has good mechanical strength and ductility.
  • Chemical stability: Hafnium remains stable and maintains its properties in various chemical environments.

How is hafnium extracted and processed?

Hafnium is extracted from minerals like zircon and baddeleyite, where it is often found together with zirconium. The extraction process typically involves the following steps:

  1. Ore concentration: The raw ore is crushed and ground to concentrate the zirconium and hafnium minerals.
  2. Separation: The concentrated minerals are treated with chemicals such as chlorine to separate zirconium from hafnium, usually through liquid-liquid extraction or ion exchange techniques.
  3. Reduction: The hafnium tetrachloride (HfCl₄) is then reduced with magnesium or sodium in a Kroll process-like setup to produce metallic hafnium.

Are there any environmental or health concerns associated with hafnium?

Hafnium is generally considered to have low toxicity, and there are few health concerns associated with its handling in industrial settings. However, fine hafnium powder can be a fire and explosion hazard due to its reactivity when finely divided. In terms of environmental impact, the extraction and processing of hafnium, like other mining and refining activities, can result in habitat disruption, water contamination, and the generation of waste products. Proper safety and environmental management practices are essential to mitigate these impacts.

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Use With Any Curriculum

These worksheets have been specifically designed for use with any international curriculum. You can use these worksheets as-is, or edit them using Google Slides to make them more specific to your own student ability levels and curriculum standards.

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