Nitride - N³⁻

What is Nitride?

Nitride is a compound of nitrogen which never comes across a protic solution. The nitrogen has an oxidation state of −3. It has an ionic radius of approximately 140 pm. Nitride contains a nitride ion (N³⁻). They can be classified into three general categories viz ionic, covalent, and interstitial.

Particular metal nitrides are unstable and react with water to form ammonia and the oxide or hydroxide of the metal; but the nitrides of boron, vanadium, silicon, titanium, and tantalum are very refractory, resistant to chemical attack, and hard—and thus are useful as abrasives and in making crucibles.

Uses of Nitride

• Silicon nitride and titanium nitride are used as hard coatings and cutting materials.
• Hexagonal boron nitride is used as a high-temperature lubricant akin to moly (molybdenum disulfide).
• Nitride compounds are used as insulators.

Preparation of nitrides

There are two methods to prepare nitrides. The first method is by direct reaction of the elements at elevated temperatures. Below is the chemical reaction for the synthesis of calcium nitride.

3Ca+N₂→Ca₃N₂

A second method is by the loss of ammonia (NH₃) by thermal decomposition of a metal amide such as barium amide.

3Ba(NH₂)₂→ Ba₃N₂ + 4NH₃

Nitrides can also be prepared by another method and that is the reduction of an oxide or metal halide in the presence of nitrogen gas. Example, the preparation of aluminium nitride.

Al₂O₃+3C+N₂→2AlN+3CO

Ionic nitrides – Lithium is the only alkali metal which is able to form a nitride, however, all the alkaline-earth metals can form nitrides with the formula M₃N₂.

Covalent nitrides – the properties depend on the element to which the nitrogen is bonded. Example, Boron nitrides – It is isoelectronic and exists in two structural forms, that are analogous forms of carbon viz diamond and graphite.

Interstitial nitride – It is the largest group of nitrides and forms the transition metals. They are similar to the interstitial carbides, where the nitrogen atoms occupy the holes or interstices, in the close-packed lattice of metal atoms. The general formula for these nitrides is MN, M₂N, and M₄N; however, their stoichiometry may vary.

Discover more about the properties, structure and applications of nitride (N³⁻) from the experts at BYJU’S.