Question

Inorganic graphite is (a) \(\mathrm{B}_{3} \mathrm{~N}_{3}\) (b) \(\mathrm{SiC}\) (c) \(\mathrm{P}_{4} \mathrm{~S}_{3}\) (d) \(\mathrm{Fe}(\mathrm{CO})_{5}\)

Short answer

The correct answer is (a) \( \mathrm{B}_{3} \mathrm{~N}_{3} \).

Step-by-step solution

Understanding Inorganic Graphite

Inorganic graphite refers to a material that exhibits similar structural properties to natural graphite, which is composed of layers of hexagonal lattices. Therefore, to solve this exercise, we need to identify which option has a similar layered structure with delocalized electrons that resemble graphite.

Option Analysis

Let's analyze each of the given options: (a) \( \mathrm{B}_{3} \mathrm{~N}_{3}\) is a part of boron nitride, known for a graphene-like hexagonal structure similar to graphite. (b) \( \mathrm{SiC}\) does not resemble graphite structurally; instead, it forms a diamond-like structure. (c) \( \mathrm{P}_{4} \mathrm{~S}_{3}\) is a molecular compound, and (d) \( \mathrm{Fe}(\mathrm{CO})_{5}\) is a metal carbonyl complex, unrelated to graphite.

Comparing Structures

Given the structure of these compounds, only boron nitride (\( \mathrm{B}_{3} \mathrm{~N}_{3}\)) forms a layered hexagonal lattice that closely mimics that of natural graphite, especially in its hexagonal version.

Conclusion

Based on the structure comparison, option (a) \( \mathrm{B}_{3} \mathrm{~N}_{3}\) is the correct answer, as it exhibits properties similar to inorganic graphite.

Key concepts

Inorganic Graphite

Inorganic graphite refers to materials that echo the structure of natural graphite. This structure is characterized by multiple layers of carbon atoms arranged in a hexagonal lattice, allowing for the existence of delocalized electrons. The electrons move freely between the layers, making graphite an excellent conductor of electricity. Inorganic graphite is not composed of carbon alone, but features materials that simulate this layered arrangement effectively. The essence of inorganic graphite lies in its ability to retain the hexagonal lattice structure found in natural graphite. This topological similarity provides it with properties that adhere to the layering found in carbon-based graphite. These properties include:

• Electrical conductivity due to delocalized electrons.
• Thermal stability across layers.
• Mechanical strength due to strong in-plane covalent bonds.

Boron Nitride

Boron nitride (BN) stands out as a prime example of inorganic graphite. Structurally, it mirrors graphite with its layers of BN hexagonal planes. This composition grants it distinct properties similar to natural graphite but also unique ones due to the BN bond. In its most prominent form, hexagonal boron nitride (h-BN), it retains a structure analogous to carbon graphite, having each nitrogen atom bonded to a boron atom, forming a repeating hexagonal pattern. The layers are strongly bonded in-plane by covalent forces, with weaker van der Waals forces holding the layers together. This enables easy sliding over one another, offering the following properties:

• High thermal conductivity.
• High chemical stability.
• White powder appearance, differing from black carbon graphite.

Boron nitride can also come in cubic form which, unlike its hexagonal form, is not like graphite and instead much resembles diamond in properties such as hardness.

Layered Structure

The concept of a layered structure is fundamental in materials that resemble graphite. This structural characteristic is where the atoms are organized in discreet yet repetitive layers, forming sheets. In materials like graphite, each layer consists of carbon atoms linked through covalent bonds to form hexagonal arrangements. These arrangements form strong in-plane bonds, contributing to the rigidity and resilience of the individual layers. What makes the layered structure particularly fascinating is not just the individual layers themselves, but the way these layers interact with each other.

• Van der Waals forces exist between layers, allowing them to slide over one another, giving graphite its lubricative properties.
• This also leads to anisotropic properties, meaning certain characteristics differ based on direction.

Layered structures contribute to the utility and versatility of materials, including their mechanical and thermal properties. In graphite-like substances, they provide resilience, toughness, and an enhanced range of applications due to their unique strength and flexibility combo.

Hexagonal Lattice

The hexagonal lattice is the quintessential geometric architecture found in materials resembling graphite. It comprises repeating hexagon shapes to create a robust yet flexible arrangement of atoms. In graphite, each layer consists of carbon atoms positioned at the vertices of hexagons. This creates strong covalent bonds within the plane of the hexagonal lattice, while maintaining weaker interactions between the layers themselves. This arrangement facilitates a high degree of durability and conductivity as well as other unique characteristics:

• It supports electron mobility across the lattice, thereby granting excellent electrical conductivity.
• The gaps between the hexagons provide flexibility and elasticity, accommodating a degree of deformation without damage.
• The structure contributes to distinct anisotropic physical properties, meaning varied hardness and electrical conductivity based on the direction of measurement.

In summary, the hexagonal lattice is critically important in defining the properties of graphite and look-alike materials, identifying them as resilient yet adaptable materials with numerous practical applications.