Carbon and its Allotropes

Which elements commonly form allotropes?

oxygen, phosphorus, sulfur, boron, carbon

Fullerenes

A molecule composed entirely of carbon in the form of a hollow sphere, ellipsoid, tube, and many other shapes. Spherical fullerenes are called buckyballs and cylindircal ones are called nanotubes. The structure is similar to that of graphite.

Graphite carbon

Allotrope of carbon with a layered, planar structure. It is the most stable arrangement of carbon, and has the highest melting point on the periodic table. In each layer, the carbon atoms are arranged in a honeycomb lattice. There are two types of graphite: alpha and beta. They differ in the stacking of the graphene layers.

Properties of allotropes

Allotropes have very different chemical and physical properties and can be transformed into each other by differences in pressure, temperature, and light.

Nanotubes

Allotropes of carbon with a cylindrical nanostructure. Extremely thermally conductive, and very toxic. Their walls are formed by one-atomic-thick sheets of graphene (incredibly strong!).

Types of Carbon

Amorphous, graphite, diamond, fullerenes, nanotubes

Uses of nanotubes

Composite fibers in polymers to improve mechanical, thermal and electrical properties of the bulk product.

Uses for Diamond

Jewelry, industrial uses such as cutting and grinding tools (diamond tipped drill bits and saws).

Diamond

Metastable allotrope of carbon where carbon atoms are arranged in a variation of the fcc crystal structure called the diamond lattice. Covalent bonds between the carbon atoms are very strong, resulting in the high hardness and thermal conductivity characteristic of diamonds. They form in high pressure, low temperature conditions. Colored diamonds result from impurities such as boron (makes it blue) and nitrogen (makes it yellow), among others.

Uses for Graphite

Refractories, batteries, steelmaking, brake linings, lubricants. Graphene naturally occurs in graphite and is a very strong substance.

Uses for Fullerenes

Tumor research

Allotropes

Different structural forms in the same phase through differences in the bonding of the atoms. The atoms involved stay the same, only the bonding is changed.

Amorphous carbon

Free, reactive carbon that does not have any crystalline structure. These samples are very porous because of the irregular arrangement of atoms. It can absorb and trap organic molecules. Ex: lump of coal.