Carbon-solid

Carbon-Solid Forms

Carbon occurs in nature in three forms, called allotropes, based on the way carbon atoms bond and arrange into a structure. The different structures give each form different physical and chemical properties. The three types of carbon allotropes are diamonds, graphite, and amorphous carbon. Carbon is also found as part of many rocks.

Diamond is one of the hardest natural materials and its strength comes from its 3-D lattice of carbon atoms. Diamonds are considered precious because they form under heat and pressure applied over the course of many years.

Graphite is the softest form of carbon and its atoms are arranged in flat layers. The layers have weak attraction and can easily slip past one another. When writing with a pencil, layers of carbon are actually rubbed off the graphite point onto the paper.

Amorphous carbon includes substances like charcoal, soot, and coke. This form consits of graphite pieces combined with small amounts of other elements, called impurities. Amorphous carbons serve as good fuel sources because they contain large amounts of carbon and will burn easily.

Rocks often contain carbon compounds in which carbon is bound to other elements. The most common compound is carbonate, where carbon bonds with calcium and magnesium. Limestone is one such rock that is made up of carbonate.

Sources:
Lutz, P. 2005. "Carbon". Microsoft Encarta Online Encyclopedia 2005.