Question

The number of closest neighbours of a carbon atom in diamond is (a) 2 (b) 4 (c) 6 (d) \(\underline{8}\)

Short answer

The number of closest neighbours of a carbon atom in diamond is 4.

Step-by-step solution

Understanding the Structure of Diamond

To solve this exercise, first understand that diamond has a crystal structure in which each carbon atom is tetrahedrally coordinated. This means that each carbon atom is bonded to four other carbon atoms.

Identifying Closest Neighbours in the Diamond Structure

By examining the crystal lattice of diamond, it is evident that each carbon atom is directly bonded to four other carbon atoms. These four atoms are at the closest distance and hence are considered the closest neighbours.

Choose the Correct Option

Based on the diamond's crystal lattice, the number of closest neighbours to a carbon atom in diamond is four. Therefore, the correct answer is (b) 4.

Key concepts

Diamond Crystal Structure

The striking beauty of diamonds isn't just skin deep—it originates from a fascinating and orderly pattern known as the diamond crystal structure. At the microscopic level, carbon atoms in diamond are arranged in a robust three-dimensional framework that bestows its famed hardness and clarity. Each carbon atom forms strong covalent bonds with four other carbons, creating a repeating pattern that extends throughout the entire crystal. This intricate web of atoms is not random but follows precise geometric rules, leading to the formation of a structure known as the 'diamond cubic' lattice.

Within this lattice, if you were to focus on a single carbon atom, you’d find it positioned in the center of a tetrahedron with bonds stretching out to four surrounding carbon atoms at the vertices. This arrangement is uniform, meaning that every carbon atom in the lattice is connected in exactly the same way, resulting in an incredibly stable and incompressible material. Thus, the characteristic strength and resilience of diamond are a direct outcome of this particular structure.

Tetrahedral Coordination in Diamond

Diving deeper into this elegant structure, we can examine the concept of tetrahedral coordination. Imagine four equidistant points forming a pyramid with a triangular base—that's a tetrahedron. In a diamond, a carbon atom sits at each of these points, including the central atom that's bonded to all others. The bond angles are perfect; each angle measures about 109.5 degrees, giving the molecule symmetric stability that contributes to the diamond's properties.

In terms of chemical bonding, these covalent bonds are extremely strong due to the sharing of electrons between carbon atoms, making diamonds the hardest known natural material. This tetrahedral coordination is also pivotal for the diamond’s optical qualities. The uniformity in the way carbon atoms are arranged allows light to travel through the crystal in predictable ways, resulting in diamond's signature brilliance and sparkle. Therefore, it's not just the chemical bonds but also the geometry of those bonds that make diamonds stand out from other materials.

Crystal Lattice

Crystal lattice is a term that can be intimidating at first glance, but it simply refers to the three-dimensional arrangement of atoms or molecules in a crystal. It's like a blueprint that nature follows to stack up tiny building blocks into a macroscopic structure that we can see and touch. If you've ever played with building blocks and created a repeating pattern, you've essentially modelled the basics of a crystal lattice concept.

The lattice in a diamond forms a very precise and repeating pattern that is characterized by its symmetry and rigidity. In the context of a diamond, every carbon atom occupies a fixed position within this lattice and is joined to its nearest neighbours in a consistently repeating pattern. This spatial organization not only determines the physical and optical properties of the crystal but also how it interacts with other elements and compounds, how it conducts heat, and how it refracts and reflects light. The beauty and utility of crystalline structures, hence, are as much a product of their microscopic lattice arrangements as they are of the atoms that comprise them.