Structure & Bonding of Carbon

What term describes different structural forms of the same element in the same physical state, such as diamond and graphite for carbon?

Allotropes.

In the giant covalent structure of diamond, how many other carbon atoms is each carbon atom bonded to?

Each carbon atom is covalently bonded to four other carbon atoms.

What type of structure does diamond have?

A giant covalent structure, specifically a regular tetrahedral network.

Why does diamond have a very high melting point?

Because a large amount of energy is needed to break the many strong covalent bonds throughout its giant structure.

Explain why diamond does not conduct electricity.

Diamond has no free or delocalised electrons to move and carry an electrical charge; all outer electrons are used in covalent bonds.

What property of diamond makes it useful for cutting tools, such as oil rig drills and glass cutters?

It is very hard, due to the rigid network of atoms held by strong covalent bonds.

In the structure of graphite, how many other carbon atoms is each carbon atom bonded to?

Each carbon atom forms three covalent bonds with other carbon atoms.

How are the carbon atoms in graphite arranged?

They form layers of hexagonal rings.

What kind of forces exist between the layers in graphite?

There are weak intermolecular forces between the layers, with no covalent bonds.

Why is graphite soft and slippery?

The layers of hexagonal rings can slide over each other because the forces between them are weak.

A key use of graphite is as a lubricant. Which structural feature allows for this?

The ability of its layers to slide over one another.

Explain why graphite can conduct electricity.

Each carbon atom has one non-bonded, delocalised electron that is free to move between the layers and carry a charge.

Despite being soft, why does graphite have a very high melting point?

Because the covalent bonds within the layers are very strong and require a great deal of energy to break.

What is graphene?

A single layer of graphite, consisting of carbon atoms joined in hexagonal rings and being only one atom thick.

Why is graphene very strong and has a high melting point?

Due to the strong covalent bonds between its carbon atoms.

Like graphite, graphene conducts electricity well because it has _____ electrons that are free to move across its surface.

delocalised

What are fullerenes?

Molecules of carbon atoms with hollow shapes, such as spheres or tubes.

The structures of fullerenes are based on hexagonal rings of carbon atoms, but what other shapes of rings can they contain?

They may also contain rings with five or seven carbon atoms.

What was the first fullerene to be discovered, and what is its chemical formula?

Buckminsterfullerene, with the formula C₆₀.

Describe the molecular structure of buckminsterfullerene (C₆₀).

Its molecules are made of 60 carbon atoms joined by covalent bonds to form a hollow sphere.

Why does buckminsterfullerene have a low melting point and is slippery?

Because there are weak intermolecular forces between its molecules which require little energy to overcome.

Fullerenes are classified as large molecules, not giant covalent structures like diamond or graphene. What is the key difference?

Fullerenes are distinct molecules with weak forces between them, whereas giant covalent structures are a continuous lattice of covalently bonded atoms.

What is a carbon nanotube?

A cylindrical fullerene, which can be imagined as a layer of graphene rolled into a tube.

Carbon nanotubes are described as having a high length to diameter ratio. What does this mean?

They are very long and thin.

What property of nanotubes makes them useful for reinforcing materials like tennis rackets?

They have a high tensile strength, meaning they are strong when stretched.

Why are carbon nanotubes good conductors of electricity?

They have delocalised electrons, similar to graphene.

Name a potential use for fullerenes that involves their hollow cage-like structure.

To deliver drugs to specific areas of the body.

What property allows fullerenes to be used as industrial catalysts?

They have a large surface area to volume ratio.

Compare the number of covalent bonds per carbon atom in diamond versus graphite.

In diamond, each carbon atom forms four covalent bonds; in graphite, each forms three.

Which allotrope of carbon is used for electrodes in batteries and electrolysis?

Graphite, because it can conduct electricity.

What structural feature is shared between graphite and graphene?

Both consist of carbon atoms arranged in layers of hexagonal rings.

Buckminsterfullerene (C₆₀) is a _____.

fullerene

The forces between buckminsterfullerene molecules are _____, while the bonds within the molecules are strong covalent bonds.

weak intermolecular forces

Graphene's properties make it useful in electronics and for making _____ materials.

composite

What makes graphite similar to metals in terms of electrical conductivity?

Both have delocalised electrons that are free to move and carry charge.

The rigid, tetrahedral arrangement of carbon atoms in _____ is responsible for its exceptional hardness.

diamond

The ability of layers to slide in graphite is due to the absence of _____ between the layers.

covalent bonds

How can the hollow shape of fullerene molecules be useful in medicine?

They can be used to form cages around other molecules, such as drugs, for delivery within the body.

Which allotrope of carbon consists of a single sheet of atoms?

Graphene.

Why can carbon nanotubes add strength to a material without adding much weight?

Because of their very high length to diameter ratio (they are long and thin).