Problem 101 - Chemistry: The Central Science in SI Units, Global Edition

Question

Which statement correctly describes a difference between graphene and graphite? (a) Graphene is a molecule but graphite is not. (b) Graphene is a single sheet of carbon atoms and graphite contains many, and larger, sheets of carbon atoms. (c) Graphene is an insulator but graphite is a metal. (d) Graphite is pure carbon but graphene is not. \((\mathbf{e})\) The carbons are \(s p^{2}\) hybridized in graphene but \(s p^{3}\) hybridized in graphite.

Step-by-Step Solution

Answer

(b) Graphene is a single sheet of carbon atoms and graphite contains many, and larger, sheets of carbon atoms.

Step 1: Option (a): Graphene is a molecule but graphite is not.

This statement isn't accurate. Graphene is a single layer of carbon atoms arranged in a hexagonal lattice, and it's a building block of graphite. Both graphene and graphite are made up of carbon atoms, but they have different structures.

Step 2: Option (b): Graphene is a single sheet of carbon atoms and graphite contains many, and larger, sheets of carbon atoms.

This statement is accurate. Graphene indeed is a single layer of carbon atoms arranged in a hexagonal lattice. Graphite, on the other hand, is made up of many layers (sheets) of graphene tightly stacked on top of one another.

Step 3: Option (c): Graphene is an insulator but graphite is a metal.

This statement is not accurate. Both graphene and graphite are good conductors of electricity, so neither is an insulator. However, it is important to note that graphite is not considered a metal, but rather a semi-metal or a good electrical conductor.

Step 4: Option (d): Graphite is pure carbon but graphene is not.

This statement is not accurate. Both graphene and graphite consist solely of carbon atoms with different arrangements. Graphene has a hexagonal lattice arrangement, while graphite consists of multiple layers of graphene stacked together.

Step 5: Option (e): The carbons are \(sp^{2}\) hybridized in graphene but \(sp^{3}\) hybridized in graphite.

This statement is not accurate. The carbon atoms in both graphene and graphite are \(sp^{2}\) hybridized. The \(sp^{2}\) hybridization in graphene and graphite allows the formation of a hexagonal lattice structure and a planar, stable configuration. Taking the analysis into account: The correct statement that describes the difference between graphene and graphite is:

Step 6: Answer

(b) Graphene is a single sheet of carbon atoms and graphite contains many, and larger, sheets of carbon atoms.

Key Concepts

Carbon Allotropes

Carbon allotropes refer to different structural forms of carbon, where atoms are bonded in various configurations. These allotropes showcase carbon's versatility and its ability to form different structures with unique properties. Two well-known carbon allotropes are graphite and graphene.
Graphene consists of a single layer of carbon atoms, arranged in a two-dimensional honeycomb lattice. It is often celebrated for its remarkable electrical, mechanical, and thermal properties.

• Graphite: A more common and naturally occurring allotrope, graphite is made of multiple graphene layers stacked together.
• Diamonds: An allotrope where carbon atoms are bonded in a three-dimensional tetrahedral structure, resulting in a very hard material.

Each allotrope illustrates the ability of carbon atoms to bond in different spatial arrangements, leading to significant changes in their physical and chemical properties. Graphene serves as the building block for graphite, and understanding their relationship helps in comprehending the structural nature of carbon materials.

Hybridization

Hybridization in chemistry is a concept where atomic orbitals mix to form new hybrid orbitals. This mixing is crucial for understanding the bonding and geometry of molecules. When we talk about graphene and graphite, both feature carbon atoms that undergo sp² hybridization.
Sp² hybridization involves:

• Mixing one s orbital with two p orbitals: This mixing creates three sp² hybrid orbitals.
• Planar Structure: The geometry of sp² hybridization gives rise to a trigonal planar structure with approximately 120° angles between the orbitals.
• Double Bonds: This hybridization allows carbon to form three sigma bonds and a pi bond, which is essential for the delocalized electron cloud in graphene.

The unhybridized p orbital in sp² forms pi bonds, contributing to the electrical conductivity of both graphene and graphite. Thus, the sp² hybridization in these materials results in their planar hexagonal lattice configurations.

Electrical Conductivity

Electrical conductivity refers to a material's ability to carry an electric current, which is influenced by the arrangement and movement of electrons within the material. Both graphene and graphite exhibit high electrical conductivity due to delocalized electrons.
Features of electrical conductivity in graphene and graphite include:

• Delocalized Electrons: In graphene, electrons can move freely across its single layer due to its sp² hybridized structure, allowing excellent conductivity.
• Layered Structure of Graphite: The layered nature of graphite, comprising many sheets of graphene, also facilitates the flow of electrons between layers.
• Applications: Their conductivity makes both materials valuable in electronics, such as in flexible displays, batteries, and transistors.

These remarkable electrical properties of graphene and graphite are largely due to their unique atomic arrangements and bonding, showcasing how structural differences can lead to varying degrees of electrical performance in carbon allotropes.