Carbon is the sixth element on the periodic table and is famous for forming the backbone of molecules found in fuels and in all living organisms. Aside from biological molecules, carbon can also be found in nature in pure mineral form. Depending on the shapes in which the carbon atoms are bonded, pure carbon can take on many forms. In diamond, each carbon atom is bonded tetrahedrally to its four nearest carbon atoms. This tightly packed arrangement of carbon atoms makes diamond the hardest naturally occurring material on earth Why is lead used in pencils even though lead is poisonous?