Interstitial Compounds

Most such compounds are made when the elements react with any transition metals. Because transition metals have vacant spaces inside them, usually occupied and filled by small atoms, making them compounds strong and rigid.

What are Interstitial Compounds?

Interstitial compounds are those compounds or alloys formed when the atom of a smaller radius gets trapped in the interstitial space/ hole of a metal lattice. These atoms can be atoms with a smaller radius like Hydrogen, Nitrogen, Carbon, etc., that settle in the crystal lattices of metals called interstitial compounds.

Classification

Transition metals have very similar lattices and they crystallise in 2 different structures: Hexagonally Close-Packed (HCC) and Face-Centred Cubical (FCC).
They are classified by two types of holes –

• Two tetrahedral holes per metal atom: This is when there is a hole in between four metal atoms.
• One octahedral hole in every metal atom: This is when there is a hole in between every six metal atoms.

Interstitial compounds are industrially important elements. These compounds are the combination of the large transition metals, such as manganese, iron, cobalt, etc., with the small metalloids, such as hydrogen, boron, carbon, etc. Now that we’ve looked into what interstitial compounds are, let us explore the properties of interstitial compounds.

The Chemical and Physical Properties of Interstitial Compounds

Interstitial compounds have several chemical and physical properties.

Chemical properties:

• The interstitial compounds are chemically inert.
• The chemical properties of such compounds are very similar to the parent metals, i.e. the transition metals. Some compounds containing or involving carbon, such as diamond, are chemically inert and do not undergo any chemical change.

Physical Properties

• The malleability and ductility are changed in these compounds. These compounds are highly malleable and are very good conductors of heat and electricity.
• One of the properties of interstitial compounds is that they have a lower density than the parent metal.
• Interstitial compounds containing elements, such as hydrogen, are powerful reducing agents.
• Such compounds are very hard. They show metallic properties like electrical and thermal conductivity, malleability, etc.
• One of the peculiar properties of interstitial compounds is that they have a very elevated melting point, higher than the melting points of pure metals or the parent metal. They have an elevated melting point because of the type of bonds that it includes. Interstitial compounds are composed of a metal-nonmetal bond which is much stronger than the usual metal-metal bond.

Example of Interstitial Compounds

Some of the examples of interstitial compounds are TiC (Titanium carbide), ZrH_1.92 (Zirconium hydride), Mn₄N (Manganese nitride), etc. TiC or Titanium carbide is an extremely hard compound. Titanium carbide shows properties such as chemical inertness and is a very good conductor. This compound has a tensile strength of 310 MPa and is used to prepare cermets. It is one of the hardest natural materials and is extensively used for cutting tools because of its wear resistance and high hardness. Titanium products are now being used in aerospace due to their lightweight, low density and other similar interstitial compound properties.
Iron Carbide (Fe₃C) is another similar example of such a compound. It is commonly called Cementite and is a compound of iron and carbon. It is primarily used in steelmaking.

Conclusion

Interstitial compounds are extremely useful compounds that have a wide application both chemically and industrially. They are formed primarily because the atoms of smaller sizes get trapped in gaps or holes inside the much bigger transition metals.
Since they’re a combination of different atoms, they possess specific properties like tensile strength, ductility, malleability, good conductivity, etc., making them a favourable compound to work with.
They are usually chemically inert, making them a better substitute for usual metals. All these properties make interstitial compounds valuable to the industrial sector.