How Are Nitrides Formed? Methods, Examples, and Key Applications
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In Chemistry, nitride is defined as the compound of nitrogen in which nitrogen has a formal oxidation state of three. A large class of compounds that has a wide range of properties and applications is called nitrides.
Nitride is composed of different classes of chemical compounds which are combined with an element of equal or lower electronegativity , like boron, silicon and other such metals.
It contains the nitrite ion (N3−). also like carbides, we can divide nitrides into three general categories , that are :
Ionic
Interstitial and
Covalent
There are few metal nitrides that are unstable and most of them react with water to form ammonia and oxide or hydroxide the metal. Some nitrides are very refractory like the nitrite of boron, vanadium, silicon, titanium and tantalum . These nitrides are also resistant to chemical attack, and therefore they are useful as abrasives and creating crucibles.
Chemistry is a very tricky subject and some students may find it difficult but if they choose the right pattern to study then they will see that the topics will be easy for you. Mainly the revision notes which the student prepares to play a very important role as in Chemistry there are numerous formulas and equations which students need to learn so the revision notes must be prepared accordingly to help students to go through it multiple times.
What is Nitride Ion?
The first question is, what is nitride and its properties. When nitrogen combines with elements such as silicon, boron, any other metals, or any element with lower or similar electronegativity than nitrogen, it is known as a nitride. It is a separate class of compounds altogether. Nitride, just like carbides, can be separated into three general categories known as interstitial, ionic, and covalent nitrides. Nitride compounds generally contain the nitride ion. Now questions such as what is the formula for nitride, what is the charge of nitride, what is the symbol of nitride are bound to arise. We will answer these questions a bit later. Such compounds usually react with water to turn into the hydroxide or oxide of the metal and ammonia gas.
Nitride Ion Overview
The question of what is nitride can be explained better by saying that it never comes through an aprotic solution. It is mainly a nitrogen compound. The Ionic radius of nitrides is 140 pm approximately. The oxidation state of nitrogen is -3. Nitride ion is the main iron present in nitrides along with the metal cation. Another question that comes is what is the formula for nitride Ion. The formula for nitride Ion is N-3. Some metal nitrates are very unstable. At the same time, some metal nitrides like those of vanadium, boron, silicon, tantalum, titanium and more are refractory. These are also resistant to earth chemical interactions and are very hard. Uses of nitride are seen in crucibles and abrasives due to hardness.
Preparation of Nitrides
There are three methods for the preparation of nitrides. The first method is where elements directly combine or reaction proceeds at higher temperatures. Calcium nitride synthesis is shown below with the direct combination method.
\[ 3C_{a} + N_{2} \rightarrow Ca_{3}N_{2} \]
The second method is a much more feasible one and is by loss of ammonia or NH3. It is done by the thermal breakdown of decomposition of barium amide or any metal amides available.
\[ 3Ba(NH_{2})_{2} \rightarrow B{a}_{3}N_{2} + 4NH_{3} \]
The method is also an easy one to proceed with in the future. During the surface hardening of metal objects, preferably steel, nitride is also formed. Ammonia when heated to high temperatures between 950 to 1050 Fahrenheit or 500 to 570 Celsius for almost 100 hours starting from a minimum of 5 hours gives out nitride. But it also depends on the desired hardening form or case's depth.
Reduction of metal oxides is metal halides that also produce nitride. It is another method to prepare nitrides and know exactly what is a nitride. The process takes place in the presence of gaseous nitrogen. Let's take an example and prepare aluminum nitride with this method.
\[ Al_{2}O_{3} + N_{2} \rightarrow 2AIN + 3CO \]
Uses of Nitride
There are many uses of nitride, but mainly they are used as insulators. One of the lubricants at high temperatures is hexagonal boron nitride which is extremely hard. The lubricating nature is due to its layered structure. It is akin to molybdenum disulfide. Nitrides are also used for cutting materials and hard coatings. For example, titanium nitride and silicon nitride are used for the same. It is because similar to carbides, nitride has high lattice energy and hence are generally refractory substances. The N-3 ions have a strong attraction with the metal cations. Owing to the large band gaps, nitride behaves like insulators. Blue light emitted from LED lights is due to the excessive bandgap in gallium nitride. Some nitrides like lithium nitride are also used for hydrogen storage purposes as they can absorb hydrogen-like metal oxides.
Ionic Nitrides
The only alkali metal that does form a nitride is Lithium. Every alkaline Earth metal forms nitrides. The formula they have is M3N2. These nitrides react with water (hydrolysis) and produce metal hydroxide and ammonia. Ionic Nitrides have a wide range of stability. Be3N2 has a melting point of 2200 degrees Celsius, and Mg3N2 at 270 degrees Celsius decomposes completely.
Interstitial Nitrides
Transition metals with nitrogen form interstitial Nitrides. Nitrogen atoms occupy holes or spaces in the closely packed lattice of the metal. The formula they have is M2N, M4N and MN. These have a metallic luster and are opaque with high conductivity, melting point and are extremely hard. Interstitial Nitrides are inert and prepared by heating the metal in ammonia. One of the characteristics reaction is giving below:
\[ 2VN + 3H_{2}SO_{4} \rightarrow V_{2}(SO_{4})_{3} + N_{2} + 3H_{2} \]
Covalent Nitrides
Examples are Cyanogen, boron nitride, disulfur dinitride, tetrasulfur tetranitride and phosphorus nitride. They have a wide range of properties.
Solved Examples
1. What is the Formula for Nitride?
Answer: What is the formula of nitride ion is a very common question. The formula is (N-3).
2. What is the Symbol for Nitride?
Answer: The symbol of the nitride ion is N-3 while metal Nitrides are of many symbols and notations.
FAQs on Nitride: Preparation, Properties, and Uses
1. What is a nitride, and what is the typical oxidation state of nitrogen in these compounds?
A nitride is a chemical compound in which nitrogen is combined with an element of similar or lower electronegativity. In most nitrides, especially ionic ones, nitrogen exists in a -3 oxidation state as the nitride ion (N³⁻). These compounds are formed with a wide range of elements, including metals, nonmetals, and metalloids, leading to vastly different properties.
2. What are the three main classifications of nitrides based on their chemical bonding?
Nitrides are broadly classified into three categories based on their primary bonding characteristics:
Ionic Nitrides: Formed with highly electropositive metals like alkali and alkaline earth metals (e.g., Li₃N, Mg₃N₂). They contain the nitride ion (N³⁻) and react with water to produce ammonia.
Covalent Nitrides: Formed with elements of similar electronegativity, such as boron (BN), silicon (Si₃N₄), and phosphorus (P₃N₅). They have strong covalent bonds, forming giant molecular structures that are very hard and chemically inert.
Interstitial Nitrides: Formed with transition metals (e.g., TiN, Fe₂N). In these, small nitrogen atoms occupy the empty spaces or 'interstices' in the metallic lattice. They are extremely hard, have very high melting points, and retain metallic conductivity.
3. How are nitrides generally prepared?
The preparation method for nitrides depends on the type of nitride desired. Common methods include:
Direct reaction with nitrogen: Heating a metal or element to a high temperature in the presence of pure nitrogen gas. For example, magnesium reacts with nitrogen to form magnesium nitride: 3Mg(s) + N₂(g) → Mg₃N₂(s).
Reaction with ammonia: Passing ammonia gas over a heated metal. This method is often used when direct reaction with N₂ is too slow. For example: 3Ca(s) + 2NH₃(g) → Ca₃N₂(s) + 3H₂(g).
4. What are the most significant physical and chemical properties of nitrides?
The properties of nitrides vary significantly with their classification. Key general properties include:
Hardness: Covalent and interstitial nitrides are among the hardest materials known, making them suitable for abrasives and cutting tools.
High Melting Points: The strong bonding in covalent and interstitial nitrides gives them exceptionally high melting points and thermal stability.
Chemical Inertness: Covalent nitrides like Boron Nitride (BN) and Silicon Nitride (Si₃N₄) are highly resistant to chemical attack.
Reactivity with Water: Ionic nitrides react readily with water (hydrolyse) to liberate ammonia gas, a key identifying chemical property.
5. What are some important industrial applications and uses of nitride compounds?
The unique properties of nitrides make them valuable in various high-performance applications:
Cutting Tools and Coatings: Titanium Nitride (TiN) is used as a hard, corrosion-resistant coating on drill bits, milling cutters, and other tools to extend their lifespan.
Ceramics: Silicon Nitride (Si₃N₄) is used to produce high-strength, thermally stable ceramic parts, such as components for automotive engines and ball bearings.
Lubricants: Hexagonal Boron Nitride (h-BN) has a layered structure similar to graphite and is used as a high-temperature solid lubricant.
Insulators: Boron Nitride is an excellent electrical insulator and is used in electronics and high-temperature equipment.
6. How do ionic, covalent, and interstitial nitrides fundamentally differ in their structure and reactivity?
The fundamental differences lie in their bonding and its consequences. Ionic nitrides involve a complete transfer of electrons to form a crystal lattice of metal cations and N³⁻ anions; this ionic nature makes them highly reactive with water. Covalent nitrides feature a network of strong, directional covalent bonds, creating giant, stable molecules that are hard and chemically inert. Interstitial nitrides are unique because nitrogen atoms fit into the voids of a metallic lattice without significantly altering the metal's structure, leading to a hybrid of metallic properties (conductivity) and ceramic-like properties (hardness).
7. Why are many interstitial nitrides, such as Titanium Nitride (TiN), known for being extremely hard and having high melting points?
The exceptional hardness and high melting points of interstitial nitrides arise from their unique structure. The small nitrogen atoms fit into the empty spaces (interstices) within the transition metal's crystal lattice. This forms strong, directional covalent-like bonds between the nitrogen and surrounding metal atoms. These bonds lock the metallic layers in place, preventing them from slipping over one another, which is the mechanism for deformation in pure metals. Breaking these strong, interlocking bonds requires immense energy, resulting in extreme hardness and a very high melting point.
8. What is the difference between a nitride ion (N³⁻) and a nitrogen molecule (N₂), and why is this crucial in understanding their chemistry?
The distinction is critical. The nitride ion (N³⁻) is a highly reactive, monoatomic anion with three extra electrons, found within the structure of ionic compounds like Mg₃N₂. In contrast, the nitrogen molecule (N₂) is a neutral, diatomic molecule that constitutes about 78% of our atmosphere. It is exceptionally stable and unreactive due to the very strong triple bond between its two nitrogen atoms. This difference explains why N₂ gas is inert under normal conditions, while ionic nitrides react readily, for example, with water to form ammonia.
9. Why is hexagonal Boron Nitride (h-BN) often referred to as 'inorganic graphite'?
Hexagonal Boron Nitride (h-BN) is called 'inorganic graphite' because of its striking structural similarity to graphite. Both materials have a layered hexagonal structure, where atoms are strongly bonded within each layer but the layers are held by weak van der Waals forces. This allows the layers to slide easily over each other, making both excellent solid lubricants. However, the key difference is in their electrical properties: graphite is a conductor because of its delocalised pi electrons, whereas h-BN is an excellent electrical insulator because the electrons are localised in the polar B-N bonds.
