Chapter 2: Atoms, Molecules, and LifeBizarre Facts in Biology |
Carbon Copy?
by Kelli A. Prior
Diamonds have long been prized as brilliant gemstones and the hardest known material on Earth. Diamonds are actually composed of a crystal lattice of carbon atoms. But did you know that one of the softest materials on earth, graphite, is simply a rearrangement of the carbon atoms in a diamond?
The lattice shape of the carbon in diamonds contributes to its amazing properties, including strength, durability, and the ability to disperse light. In a diamond, each carbon atom is connected to four other carbon atoms by strong chemical bonds, creating diamond's rigid crystal structure. The Mohs scale is a hardness scale developed in 1822 by Austrian Friedrich Mohs that is often used to characterize gemstones. Diamonds rate highest on this scale, with a rank of a ten.
Graphite, however, is at the exact opposite end of the Mohs scale with a score of one. The carbon atoms in graphite are layered, which forms a horizontal arrangement of stacked carbon. While the carbon atoms in a given stack are connected, the stacks themselves are not bonded together. This configuration explains why graphite is often used in pencils, as the layers of carbon atoms readily cleave off of the graphite molecule, allowing one to leave marks as they write with a graphite pencil. This alternative arrangement of carbon atoms in graphite, therefore, results in a completely different set of properties, including its relative softness.
Scientists also investigate the unique properties of other less well known compounds composed solely of carbon. These studies have provided an insight into how identical carbon atoms can be arranged into so many distinctive materials.