radioactive carbon with mass number 14 appears constantly in the lower stratosphere due to the fact that neutrons of cosmic rays affect the nitrogen nucleus.Free carbon is found in nature in the form of graphite and diamond, but the bulk of his weight falls on natural carbonates, flammable gas, coal, peat, oil, hard coal and other fossil fuels.
The Earth's crust contains about 0.48% carbon (by weight) in the hydrosphere and atmosphere, it is in the form of silica.Approximately 18% of the carbon on the planet is a part of the plants and animals.Its circulation includes biological cycle, as well as the evolution of carbon dioxide into the atmosphere during the combustion of fuel.
The biological cycle includes several stages: first, the carbon absorbed by plants from the troposphere, and then ret
urned to the biosphere from the geosphere.Together with plants of this element ingested by humans and animals, then it passes by the decay in the soil, and then in the form of carbon dioxide is sent into the atmosphere.
4 carbon atoms form strong simple, double and triple bonds, which contributes to the emergence of resistant cycles and chains, it is one of the reasons for the existence of a huge number of carbon-containing organic compounds.
most studied crystalline modifications of carbon - diamond and graphite.Graphite is thermodynamically stable in normal conditions, diamond, and other forms are metastable.At temperatures above 1200 ° K and atmospheric pressure, the diamond becomes graphite at 2100 K and the conversion takes a few seconds.
At normal pressure the carbon begins to sublimate, when the temperature reaches 3780 K in a liquid state, it can be only under certain external pressure.Terms of direct conversion of graphite into diamond - the pressure of 11-12 GPa and temperature of 3000 K.
carbon is chemically inert at ordinary temperatures, but at high enough it shows strong regenerative properties and is connected with many elements.Different forms of carbon is different reactivity, it decreases in the order: amorphous carbon, graphite and diamond.Amorphous carbon and graphite are reacted with hydrogen at a temperature of 1200 ° C, with fluorine - at 900C.Graphite is reacted with alkali metals and halogens to form inclusion compounds.