Does carbon exist as elementary molecules

Fascination with chemistry

Carbon is part of all living things. Less than 0.05 percent of the element occurs in the earth's crust. Nevertheless, it occupies a special position among the elements. Carbon owes its uniqueness to its ability to form bonds with other elements and, above all, with itself to form chain and ring-shaped structures. Over 45 million carbon compounds are known. This means that the number of carbon compounds is far greater than the total of all compounds of the other elements.

Forms of carbon

Carbon occurs in several different forms (modifications). Diamond is the hardest natural material we know. The largest diamond “Cullinan” was found in South Africa and is 3106 carats. - Who does not remember Marilyn Monroe's “Diamonds are a girl’s best friend”.

In the cut form (brilliant) diamond is a precious gemstone. If you heat diamond, it is transformed into the more stable, soft and black graphite at very high temperatures. Coke, charcoal, animal charcoal and soot are other forms of (partially) graphitic carbon. In addition to these modifications, there is a third one: the graphite-like fullerenes, carbon atoms arranged in 5- and 6-membered rings that build up spherical (soccer-like) structures.

Coals are complex mixtures which, in addition to carbon, also contain hydrogen, oxygen and volatile components as well as sulfur. They are important sources of energy and burn to carbon monoxide (CO) and carbon dioxide (CO2) in the air. In addition, carbon in the form of coke plays an important role in metal extraction (steel production, blast furnace process). Coals and hydrocarbon compounds (natural gas, crude oil, asphalt, bitumen) are the decay residues of organic life (plants, animals).

soot forms when carbon compounds are burned when there is insufficient air supply. It is used as a filler in rubber for car tires as well as for the production of printing ink, Indian ink and shoe polish.

Carbon fiber are valuable materials with high breaking strength, which are used, for example, in aircraft construction.

Medicine and household

In the finely divided state, carbon has an extraordinary adsorptive capacity and is used as medical charcoal to absorb toxins, bacteria and their toxins (activated charcoal).
In the mineral sector, carbon occurs mainly in the form of carbonates, the salts of carbonic acid. As limestone, marble, chalk (calcium carbonate) or as dolomite (calcium-magnesium-carbonate), carbonates can build up entire mountains. In the past, soda (sodium carbonate, "carbonated sodium") was used in the household as a washing and cleaning agent, and it was also used to soften water.
 

Symbol for the interplay of inanimate and animate world

Bound in carbon dioxide (CO2) carbon is also found in the air, large amounts of which are in dissolved form in seawater. The determination of the content of radioactive C14 carbon is used to determine the age of fossil finds (radiocarbon method).

In the plant and animal kingdoms, the element carbon forms the basic building block of all molecules. That is why carbon compounds are also referred to as "organic molecules". The carbon cycle is an important part of our earth's ecosystem; it stands for the interplay of inanimate and animate world. The writer Primo Levi described this cycle impressively in the "History of a Carbon Atom", here abbreviated:
“For millions of years, the carbon atom - (C) has been the limestone rock (CaCO3) exists before it is mined with a pickaxe one day, heated in the lime kiln and separated from the lime (CaO) as carbon dioxide (CO2) flies out of the chimney. It travels with the wind, dissolves in water, is released again, one day brushes the leaf of a vine it penetrates. There it collides with large and small molecules and with the help of light and leaf green (photosynthesis) is incorporated into a sugar molecule (glucose). It then migrates in the sap from the leaf over the stem and trunk into a grape, gets into the wine and is drunk. It lingers in the wine drinker's liver for a while. The glucose is then used for hard work, transported via the bloodstream into a muscle fiber, where it is broken down into two molecules of lactic acid for energy gain. With the help of the inhaled oxygen, the lactic acid and a carbon dioxide molecule (CO2) returns to the atmosphere with the air we breathe. "

This closes the carbon cycle. These and similar stories document the impressive role of carbon as an "element of life".

The article was created by the Public Relations Working Group of the Senior Chemistry Experts, a specialist group of the Society of German Chemists.
Authors: Prof. Dr. Eberhard Ehlers and Dr. Ursula Kraska (edited by sue)

Cover picture: Mario Sarto, Diamant tropfen, CC BY-SA 3.0

If you want to find out more about carbon, you can read on here.

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