Carbon (C), the chemical element of group-14 or Group IVA in the periodic table occurrence in nature as carbon black, activated carbon, graphite, diamond, oxide, carbonates, and emission products of living organisms. It is the key chemical element in all living organisms of our environment forms a large number of organic compounds with hydrogen which plays a crucial role in the vegetable and animal kingdom. The chemistry of carbon is unique due to p-p π-bonding. It has a strong affinity for chemical bonding with hydrogen, oxygen, or fluorine.
What is carbon cycle?
CO2 and water of our environment are worked up by plants through the agency of chlorophyll and photon rays from sunlight to form carbohydrates. Carbohydrates are taken by the animal kingdom and transfer into CO2 and H2O to form the biological cycle of carbon.
Properties of carbon
The essential element, carbon has the chemical symbol C, atomic number 6. Some physical and chemical properties of the element given below the table,
|Properties of Carbon|
|Electronic configuration||1s2 2s2 2p2|
|Melting point||4100 °C|
|Density||graphite – 2.267 g/cm3
diamond – 3.515 g/cm3
|Electrical resistivity||7.837 nΩ·m (graphite)|
|Oxidation number||+ 4|
|Electronegativity||Pauling scale – 2.55|
|Ionization energy||1st – 1086.5 kJ/mol
2nd – 2352.6 kJ/mol
3rd – 4620.5 kJ/mol
Sources of carbon
It present in the earth’s crust to the extent of about 0.08 percent and crude oil, coal, and natural gas or hydrocarbon is the most common combined form of carbon. Flakes of graphite and crystalline diamond occurs in metamorphosed sedimentary rocks like quartz.
Diamond occurs in Kimberlite (a dark color basic rock of Kimberlin found in South Africa) with ancient volcanic pipes. India and Borneo are the oldest diamond producing countries in the world. The allotrope diamond was found in Brazil in 1729 and south African deposits were discovered in the latter part of the nineteenth century.
Properties of carbon compounds
The chemistry of carbon compounds explains by their electronic configuration. It has atomic number 6 with electronic configuration 1s2 2s2 2p2. Therefore, four electrons present in the outer quantum orbital. When we have taken four ionization energy together, the value is very high. No compounds know with + 4 cations. Instead of forming ionic compounds, in most cases, the compound is formed by four covalent bonding with sp3 hybridization.
It not only forms the single covalent bonding to attain the noble gas electronic configuration. It also formed multiple bonds with sp2 and sp-hybridization in compounds like ethylene and acetylene. Naturally, it posses the + 4 oxidation number or state due to the very low electronegativity but in metal carbides like sodium carbides or calcium carbide, it posses – 4 oxidation state.
Isotopes of C-14 and C-12
The principal isotopes of carbon are C-14 and C-12 occurs in nature about 1.11 percent. These isotopes use in Fourier transform nuclear magnetic resonance (NMR-spectrum) data analysis. The atmospheric CO2 contains about 1.2 × 10-10 percent of radioactive C-14 with a half-life of 5570 years. C-14 produces by the neutron-proton reaction on nitrogen by thermal cosmic particle radiation. The ratio of C-14 and C-12 use in radiocarbon dating or the age of plants or animals.
Production of coke
Among all the natural forms, coke is used in large quantities for energy generation in our daily life. Coke is obtained by cooking or high-temperature carbonization of coal in the absence of air.
Production of graphite
Natural graphite was obtained in a mixture of mica, quartz, and silicates. The mixture was washed by flotation and heated with specific heat and hydrochloric acid and hydrofluoric acid in a vacuum. The residual silicon compounds precipitated as SiF4 molecules. Graphite is also made by heating silica with coke in an electric furnace at 2500 °C for about 24 hours.
Production of diamond
Natural allotrope like diamond uses in large quantities about 18 tones per year in industries and gems. Only small-size industrial diamonds are made synthetically by subjecting graphite to 125000 atm pressure and 3000K temperature. But if we use the metal chemical catalyst, the conversion is achieved at 70,000 atm pressure and 2000K temperature.
Production of carbon black
Carbon black prepared by incomplete thermodynamics combustion of hydrocarbon but activated carbon prepared by control pyrolysis of organic compounds like sawdust or coconut shell.
Uses of carbon
The allotope of carbon like coke is used in the extraction of iron metals and many other metals.
Uses of graphite and diamond
Graphites and diamonds are the other allotropes of carbon. Graphite mainly uses in steelmaking, metal foundries, refractories, making crucibles, nozzles, fuel cell redox electrodes, etc. It also uses highly in lubricant manufacturing plants but important use of graphite in the nuclear power reactors as neuron moderators. Diamond, a valuable gemstone uses industrially in making drills and as an abrasive for cutting and polishing.
Uses of carbon black
Carbon black largely uses in the rubber industry to increases the strength of rubber particularly those used in making car tires.
Uses of activated carbon
Activated carbon is a very efficient absorbent in chemistry uses for absorbing organic pollutants from drinking water and greenhouse gases from the air. It is largely used as a decolorizing agent in the sugar industry, gas purification, including air pollution and gas masks. Activated carbon also uses in the treatment of sewage water pollution in nature and as a chemical catalyst.