Ch.22 - The Main Group Elements

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.22 - The Main Group Elements

Problem 22.93

Chapter 22, Problem 22.93

What is the hybridization and geometry around carbon atoms in graphene? Explain why graphene is an excellent conductor of electricity.

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Graphene is a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice. Each carbon atom in graphene is bonded to three other carbon atoms.

To determine the hybridization of the carbon atoms in graphene, consider the number of sigma bonds and lone pairs around each carbon. In graphene, each carbon forms three sigma bonds with neighboring carbon atoms.

The hybridization of a carbon atom with three sigma bonds and no lone pairs is \( sp^2 \). This hybridization involves the mixing of one \( s \) orbital and two \( p \) orbitals, resulting in three \( sp^2 \) hybrid orbitals.

The geometry around each carbon atom in graphene is trigonal planar, with bond angles of approximately 120 degrees. This planar structure allows for the overlap of \( p \) orbitals, forming a delocalized \( \pi \) bond system across the entire graphene sheet.

Graphene is an excellent conductor of electricity because the delocalized \( \pi \) electrons can move freely across the entire sheet, allowing for efficient charge transport. This delocalization is a result of the \( sp^2 \) hybridization and the planar geometry of the carbon atoms.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hybridization

Hybridization is the process by which atomic orbitals mix to form new hybrid orbitals, which can explain the bonding properties of atoms in molecules. In graphene, carbon atoms undergo sp2 hybridization, where one s orbital and two p orbitals combine to create three equivalent sp2 hybrid orbitals. This arrangement allows for the formation of strong sigma bonds with neighboring carbon atoms, resulting in a planar structure.

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. In graphene, the sp2 hybridization leads to a trigonal planar geometry around each carbon atom, with bond angles of approximately 120 degrees. This planar structure contributes to the stability and unique properties of graphene, including its high strength and flexibility.

Electrical Conductivity

Electrical conductivity in materials is the ability to conduct electric current, which in graphene is attributed to its delocalized π electrons. The planar structure of graphene allows these π electrons to move freely across the lattice, facilitating the flow of electricity. This property, combined with its high electron mobility, makes graphene an excellent conductor, surpassing many traditional conductive materials.

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Describe the structure of diborane (B₂H₆) and explain why the bridging B–H bonds are longer than the terminal B–H bonds.

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Textbook Question

Why are CO and CN^– so toxic to humans?

Textbook Question

Using the shorthand notation of Figure 22.9, draw the structure of the silicate anion in:

(a) K₄SiO₄ (b) Ag₁₀Si₄O₁₃

What is the relationship between the charge on the anion and the number of terminal O atoms?

Textbook Question

List three ways in which the properties of boron differ from those of the other group 3A elements.

Textbook Question

The following pictures represent structures of the hydrides of four second-row elements:

(1)

(2)

(3)

(4)

(a) Which compound has the highest melting point?

Textbook Question

a. Why is the SO₃ molecule trigonal planar but the SO₃^2– ion is trigonal pyramidal?