Question

Boron nitridc obtained by heating borazolc is (1) white solid with a diamond-like structure. (2) slippery white solid with layered structure similar to that of graphite. (3) covalent liquid and is structurally similar to $\mathrm{CO}$. (4) soft low-melting solid with rock salt-like structure.

Short answer

Option (2) is correct: slippery white solid with a layered structure similar to graphite.

Step-by-step solution

Identify the compound formation

Boron nitride (BN) is formed by heating borazole. Recall the general properties of boron nitride.

Analyze the structure types

Consider the possible structures mentioned in the options: diamond-like structure, layered structure like graphite, covalent liquid similar to CO, and rock salt-like structure.

Compare boron nitride properties

Boron nitride typically has a structure similar to graphite, characterized by layers, making it slippery and white. It’s not similar to carbon monoxide, nor does it have a rock salt-like or diamond-like structure.

Select the correct answer

Based on the comparison, the best-matching description is a slippery white solid with a layered structure similar to graphite.

Key concepts

Boron Nitride Structure

Boron Nitride (BN) is a compound made up of boron and nitrogen atoms in a 1:1 ratio. It exhibits a variety of structures, but one of the most common forms is the hexagonal structure. In this structure, boron and nitrogen atoms are arranged in a hexagonal lattice, similar to the arrangement of carbon atoms in graphite.
Each boron atom is bonded to three nitrogen atoms, and each nitrogen atom is bonded to three boron atoms. This creates a network of strong covalent bonds within each layer of the lattice. However, the layers themselves are held together by weaker van der Waals forces. This layered arrangement plays a significant role in the material properties of boron nitride.

Layered Structure Similar to Graphite

One of the most notable characteristics of hexagonal boron nitride (h-BN) is its layered structure, which closely resembles the structure of graphite. Like graphite, h-BN is composed of layers that can easily slide over each other. This property makes h-BN slippery and an excellent lubricant.
In both h-BN and graphite, the layers are held together by weak forces known as van der Waals forces. However, the bonding within the layers is very strong due to covalent bonds. Despite the similarities, there are differences too. For instance, graphite is electrically conductive, while h-BN is an electrical insulator.
This structural similarity to graphite not only gives h-BN its notable lubricant properties but also makes it suitable for high-temperature applications.

Properties of Boron Compounds

Boron compounds, including boron nitride, exhibit a wide range of properties that make them useful in various applications. Here are some key properties of boron nitride and related boron compounds:

• Stability: Boron nitride is chemically inert and can withstand high temperatures without breaking down. This makes it useful in high-temperature and high-pressure environments.


• Thermal Conductivity: BN has excellent thermal conductivity, allowing it to dissipate heat quickly. This property is advantageous in electronics and thermal management applications.


• Electrical Insulation: Unlike graphite, hexagonal boron nitride is an excellent electrical insulator. It can be used in applications where electrical conductivity is undesired.


• Lubricant Properties: Due to its layered structure, h-BN acts as an effective lubricant, reducing friction in mechanical systems.


• Hardness: Although not as hard as diamond, cubic boron nitride (another form of BN) is one of the hardest known materials. It is used in cutting tools and abrasives.

These properties make boron nitride a versatile material with applications ranging from industrial lubricants and high-temperature insulators to components in electronics and even cosmetics.