Carbon is a chemical element with the symbol C. Its atomic number is 6. It is nonmetallic and tetravalent. it is present in the 14th group of the periodic table. It has three isotopes that are 12C, 13C, and 14C. 12C and 13C are stable. 14C is radioactive. Its half-life is 5,730 years. it is used in radiocarbon dating and radiolabeling. It is the 4th most abundant element in the universe by mass after H, He, and O. It is the second most abundant element in the human body after O. 0.025% of it is present in the earth’s crust. It can make bonds together in various ways to form allotropes of C. Diamond and graphite are the most important allotropes of it.
The word carbon comes from the Latin word carbo. This word was used for coal or charcoal.
It was discovered in prehistory. It was known in the forms of soot and charcoal. In 1772, Antoine Lavoisier proved that diamond is a form of C. He burnt samples of charcoals and diamonds. He found that both released the same amount of CO2 per gram. In 1779, Carl Wilhelm Scheele showed that graphite was identical to charcoal. In 1786, the French scientists proved that graphite was a form of carbon.
C forms many allotropes. Allotropes are different structural forms of the same element. Diamond and graphite are the most important allotropes of C. In recent decades, many more allotropes have been discovered such as buckminsterfullerene and graphene. Large structures of C are nanotube, nanobuds, and nanoribbons. Some other forms of C can exist at high temperature and pressure. According to SACADA( Samara Carbon Allotrope Database), 500 hypothetical allotropes of C are known at present.
Diamond is an allotropic form of C. It is hard and disperses light. Due to these properties, diamond is used in jewelry. In diamond, each carbon is covalently bonded to four other C atoms forming a tetrahedron structure. These tetrahedrons form three dimensional stable network. That is why a diamond is so strong. Diamond is used for cutting, drilling, grinding, and polishing.
Graphite is the most common allotropic form of it. The word graphite was named by Abraham Gottlob Werner from the Greek word graphein used for a pencil. It can conduct electricity due to the delocalization of pi electrons. These electrons can move freely above and below the planes of C atoms, so conduct electricity. Hower graphite can conduct electricity parallel to the planes, not perpendicular to the planes. Thus, it is used in electric arc lamps. In powder form, graphite is used as a dry lubricant.
It can form a long chain of C–C bonds. This property is called catenation. Tt forms a countless number of organic compounds. In most organic compounds, it is bonded to the hydrogen atom. The most important organic compounds are hydrocarbons in which the C atom is bonded to the hydrogen atom. It obeys the octet rule and is tetravalent( forming four covalent bonds) in most compounds. It is the basis of organic chemistry. The hydrocarbons are very important to the industry. These compounds are used as refrigerants, lubricants, and solvents for the manufacture of plastics and chemicals. It forms many important biological compounds such as sugars, fats, DNA, RNA, ATP, etc.
Compounds containing C that do not make bonds to the other C atoms, halogens, or hydrogen are studied separately from organic chemistry. Among these compounds, oxides of carbon are simple inorganic compounds. CO2 is the most important oxide of C. 0.04% of CO2 is present in the earth’s atmosphere. The other important oxide of C is CO. It is a colorless and odorless gas. It can be prepared by incomplete combustion. Cyanide(CN–) and cyaphide(CP–) are also considered as the most important inorganic compounds of It
The compounds in which a C atom is bonded covalently to a metal atom are called organometallic compounds. Ferrocene, Cobaltocene, Zeise’s salt, Trimethylaluminium, and Dimethylzinc are important organometallic compounds.
C is essential to all living organisms. Life is impossible without it. It is used as gasoline, kerosene, and other product. Cellulose is a natural polymer of it. It can be obtained from plants in the form of wood, cotton, linen, and hemp. Synthetic polymers are used to make plastics. When graphite is mixed with clays, it becomes lead. Lead is used in pencils which are used for drawing and writing. It is also used as lubricants and pigments.
Charcoal is used in artwork, grilling, iron smelting, barbecue, and in many other applications. Carbon black is used in the printing ink, oil paint, carbon paper, and automobile tires. C compounds are used in clothing material. Carbides of tungsten are the hardest materials. These are used as abrasives materials in cutting and grinding tools.