Carbon is a nonmetallic element, represented by the symbol 'C', and has the atomic number 6. If you take a look at the modern periodic table, you will find it amongst the group 14 elements. Chemically, it is a highly stable element. As far as its availability in the Earth's crust is concerned, it stands 15th in the most abundant elements list. When calculated in percentage value of mass, it is found as the 4th most abundant chemical element in the whole universe.
In chemistry, carbon is studied to understand the concepts of isotopes and allotropes. The former refers to occurrence of two or more atoms of the same element having different number of neutrons; whereas the latter is defined as occurrence of an element in two or more structurally different forms.
Carbon Allotropes: Explained
As mentioned already, carbon can exist in varied molecular configurations. Out of these, three allotropes are found to be abundant in nature. These include graphite, diamond, and amorphous carbon. They are formed when carbon is subjected to different conditions. Say for example; this element occurs as soft graphite under normal pressure, while it takes the form of diamond, when exposed to high pressure. The type of crystal system in graphite is hexagonal, while that of diamond is isometric.
Researches have opined that graphite is formed when carbon is exposed to normal pressure condition. Considering this, it is the most stable allotrope under normal conditions. It is soft, lightweight, and has the property to conduct electricity. It cleaves in smooth planes; the main reason being bonding of graphite flakes by weak van der Waals force. Commercially, graphite is used as a lubricant. When subjected to very high temperature and pressure, graphite can be converted into diamond.
A Diamond's high value in jewelry is a result of its unique light dispersion property. Unlike graphite, it is transparent, compact, and abrasive in nature. It is the hardest and strongest known mineral, used for commercial applications like cutting, drilling, and grinding. Diamond cannot conduct electricity; rather it is described as a good insulator. At present, scientific studies are ongoing to produce synthetic diamonds in laboratories.
As the name suggests, this allotrope is non-crystalline, and found in a powdery form. It is a major component of charcoal and soot. As you examine its detailed molecular structure, you can find small crystals similar to graphite and diamond. Thus, it is often considered as a variant form of graphite. True amorphous carbon can be synthesized under controlled conditions.
You can compare graphite and diamond, in order to understand the physical differences between these allotropic forms. In addition to the above mentioned types, other allotropes include glassy carbon, fullerenes, lonsdaleite, aggregated diamond nanorods, and carbon nanofoam. Some of these are described as exotic, with respect to their occurrence in nature.