What is the Difference Between Hafnium and Zirconium

The key difference between hafnium and zirconium is that hafnium has a comparatively low density than zirconium, which has a high density.

Hafnium and zirconium have closely similar chemical properties, as given below in this article, which makes it difficult to separate them from each other chemically.

1. Overview and Key Difference
2. What is Hafnium
3. What is Zirconium
3. Similarities Between Hafnium and Zirconium
4. Hafnium vs Zirconium in Tabular Form
5. Summary – Hafnium vs Zirconium

What is Hafnium?

Hafnium is a chemical element having the atomic number 72 and the chemical symbol Hf. It appears as a lustrous, silvery-grey metal that falls under the category of tetravalent transition metals. It chemically resembles zirconium. Therefore, we can find hafnium in many zirconium minerals as well. This metal can be found in group 4 and period 6 of the periodic table, and it exists in the d block of elements. This chemical element was found in 1923 by Coster and Hevesy as the second last stable element. The last stable element is rhenium.

Figure 01: Hafnium

At room temperature and pressure, this chemical element occurs as a solid metal, and it has high melting and boiling points as well. The most common and stable oxidation state for hafnium is +4. Naturally, it occurs in a primordial nature, and it has the crystal structure of a hexagonal close-packed structure. It is a paramagnetic metal. Moreover, it is a ductile metal that is resistant to corrosion.

Mostly, hafnium is useful in manufacturing control rods for nuclear reactors. However, the use of hafnium is very little because of its close similarity to zirconium, which makes it easily replaceable. Difficulty to separate and less abundance also makes it a scarce commodity metal. In addition, it is useful in making some alloys with iron, titanium, niobium, tantalum, etc. It is also useful in manufacturing microprocessors.

What is Zirconium?

Zirconium is a chemical element having the chemical symbol Zr and atomic number 40. The name comes from the mineral zircon, the source of zirconium. It is a lustrous, silvery-white metal that resembles hafnium. It is a transition metal. This chemical element occurs in group 4 and period 5 of the periodic table, and it is a d block element as well.

Hafnium and Zirconium - Side by Side Comparison

Figure 02: Zirconium

Zirconium is a ductile and malleable metal that exists in solid-state at room temperature and pressure. When it has impurities, the metal becomes hard and brittle. In its powder form, it is highly flammable, while the solid form is less prone to ignition. Besides, this metal is highly resistant to corrosion caused by alkalis, acids, saltwater and other agents.

When considering its applications, it is mainly useful in high-temperature applications. Moreover, it is useful as an opacifier, as moulds for molten metals, manufacture of laboratory crucibles, as a refractory material for metallurgical furnaces, as a component in some abrasives, etc.

Separation of Zirconium and Hafnium

Since zirconium metal and hafnium metal have similar chemical properties, contamination of zirconium with hafnium or vice versa is not problematic for most of their applications. However, their neutron-absorbing properties have a great difference which makes it important to separate the two metals from each other. We can use liquid-liquid extraction, fractional crystallization, extractive distillation, etc., for this separation.

What are the Similarities Between Hafnium and Zirconium?

Hafnium and zirconium have the same number of valence electrons.
They have closely similar chemical properties and reactivity.
Both have similar relativistic effects.
They are difficult to separate from each other because of chemical similarity.

What is the Difference Between Hafnium and Zirconium?

Hafnium and zirconium have closely similar chemical properties, as given below in this article, which makes it difficult to separate them from each other chemically. The key difference between hafnium and zirconium is that hafnium has comparatively a low density, whereas zirconium has a high density. Moreover, the neutron-absorption of hafnium is about 600 times greater than zirconium.

The below infographic lists the differences between hafnium and zirconium in tabular form for side by side comparison.

Summary – Hafnium vs Zirconium

Hafnium and zirconium are transition metals. They resemble each other because they have similar chemical properties. The key difference between hafnium and zirconium is that hafnium has comparatively a low density, whereas zirconium has a high density.

Reference:

1. “Zirconium.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine.

Image Courtesy:

1. “Hf-crystal bar” By Alchemist-hp (talk) (www.pse-mendelejew.de) – Own work (CC BY-SA 3.0 de) via Commons Wikimedia
2. “Zirconium crystal bar and 1cm3 cube” By Alchemist-hp (pse-mendelejew.de). – Own work (FAL) via Commons Wikimedia