CARBON IN NATURE: LOCATION, PROPERTIES AND USES - GEOGRAFÍA - 2025

The carbon in nature can be found in diamonds, oil and graphites, among many other scenarios. This chemical element occupies the sixth place in the periodic table and is located in the horizontal row or period 2 and column 14. It is non-metallic and tetravalent; that is, it can establish 4 shared electron chemical bonds or covalent bonds.

Carbon is the most abundant element in the earth's crust. This abundance, its unique diversity in the formation of organic compounds and its exceptional ability to form macromolecules or polymers at temperatures commonly found on Earth, makes it serve as a common element of all known life forms.

Figure 1. Carbon in its mineral form. Source: Rdamian1234, from Wikimedia Commons

Carbon exists in nature as a chemical element without combining in the forms of graphite and diamond. However, for the most part it is combined to form carbon chemical compounds, such as calcium carbonate (CaCO ₃) and other compounds in oil and natural gas.

It also forms various minerals such as anthracite, coal, lignite, and peat. The greatest importance of carbon is that it constitutes the so-called “building block of life” and is present in all living organisms.

Where is carbon found and in what form?

In addition to being the common component chemical element in all forms of life, carbon in nature is present in three crystalline forms: diamond, graphite, and fullerene.

There are also several amorphous mineral forms of coal (anthracite, lignite, coal, peat), liquid forms (oil varieties) and gaseous (natural gas).

Crystalline forms

In crystalline forms, carbon atoms join to form ordered patterns with geometric spatial arrangement.

Graphite

It is a soft black solid with a metallic luster or luster and heat resistant (refractory). Its crystalline structure presents carbon atoms joined in hexagonal rings that, in turn, join forming sheets.

Graphite deposits are rare and have been found in China, India, Brazil, North Korea, and Canada.

Diamond

It is a very hard solid, transparent to the passage of light and much denser than graphite: the value of the density of diamond is almost twice that of graphite.

The carbon atoms in the diamond are joined together in tetrahedral geometry. Likewise, diamond is formed from graphite subjected to conditions of very high temperatures and pressures (3,000 ^° C and 100,000 atm).

Most of the diamonds are located between 140 and 190 km deep in the mantle. Through deep volcanic eruptions, magma can transport them to distances close to the surface.

There are diamond deposits in Africa (Namibia, Ghana, Democratic Republic of the Congo, Sierra Leone and South Africa), America (Brazil, Colombia, Venezuela, Guyana, Peru), Oceania (Australia) and Asia (India).

Figure 3. Coal and diamond. Source: XAVI999, from Wikimedia Commons.

Fullerenes

They are molecular forms of carbon that form clusters of 60 and 70 carbon atoms in almost spherical molecules, similar to soccer balls.

There are also smaller fullerenes of 20 carbon atoms. Some forms of fullerenes include carbon nanotubes and carbon fibers.

Figure 4. Fullerene. IMeowbot, via Wikimedia Commons

Amorphous forms

In amorphous forms, the carbon atoms do not unite, constituting an ordered and regular crystalline structure. Instead, they even contain impurities from other elements.

Anthracite

It is the oldest metamorphic mineral coal (which comes from the modification of rocks by effects of temperature, pressure or chemical action of fluids), since its formation dates from the primary or Paleozoic era, the Carboniferous period.

Anthracite is the amorphous form of carbon with the highest content of this element: between 86 and 95%. It is gray-black in color with a metallic luster, and it is heavy and compact.

Anthracite is generally found in geological deformation zones and constitutes about 1% of the world's coal reserves.

Geographically it is found in Canada, USA, South Africa, France, Great Britain, Germany, Russia, China, Australia and Colombia.

Figure 5. Anthracite, the oldest coal with the highest carbon content. Educerva, from Wikimedia Commons

Coal

It is a mineral coal, a sedimentary rock of organic origin, whose formation dates from the Paleozoic and Mesozoic eras. It has a carbon content of between 75 and 85%.

It is black in color, characterized by being opaque and having a matte and greasy appearance, as it has a high content of bituminous substances. It is formed by compression of lignite in the Paleozoic era, in the Carboniferous and Permian periods.

It is the most abundant form of carbon on the planet. There are large coal deposits in the United States, Great Britain, Germany, Russia, and China.

Lignite

It is a mineral fossil coal formed in the Tertiary era from peat by compression (high pressures). It has a lower carbon content than coal, between 70 and 80%.

It is a slightly compact material, crumbly (a characteristic that distinguishes it from other carbon minerals), brown or black in color. Its texture is similar to that of wood and its carbon content ranges from 60 to 75%.

It is an easy-to-ignite fuel, with a low calorific value and a lower water content than peat.

There are important lignite mines in Germany, Russia, the Czech Republic, Italy (Veneto, Tuscany, Umbria regions) and Sardinia. In Spain, the lignite deposits are in Asturias, Andorra, Zaragoza and La Coruña.

Peat

It is a material of organic origin whose formation comes from the Quaternary era, much more recent than previous coals.

It is brownish yellow in color and appears in the form of a low-density spongy mass, in which you can see plant remains from the place where it originated.

Unlike the coals mentioned above, peat does not come from carbonization processes of woody material or wood, but has been formed by the accumulation of plants -mainly grasses and mosses- in swampy areas through a carbonization process that has not been completed..

Peat has a high water content; for this reason it requires drying and compaction before use.

It has a low carbon content (only 55%); therefore, it has a low energy value. When subjected to combustion, its ash residue is abundant and it emits a lot of smoke.

There are important deposits of peat in Chile, Argentina (Tierra del Fuego), Spain (Espinosa de Cerrato, Palencia), Germany, Denmark, Holland, Russia, France.

Figure 6. Peat reservoir. Christian Fischer, from Wikimedia Commons

Oil, natural gas and bitumen

Petroleum (from the Latin petrae, which means "stone"; and oleum, which means "oil": "rock oil") is a mixture of many organic compounds - most of them hydrocarbons - produced by anaerobic bacterial decomposition (in the absence of oxygen) of organic matter.

It was formed in the subsoil, at great depths and under special conditions both physical (high pressures and temperatures) and chemical (presence of specific catalyst compounds) in a process that took millions of years.

During this process, C and H were released from the organic tissues and joined, recombining again, to form an immense number of hydrocarbons that mix according to their properties, forming natural gas, oil and bitumen.

The world's oil fields are located mainly in Venezuela, Saudi Arabia, Iraq, Iran, Kuwait, the United Arab Emirates, Russia, Libya, Nigeria and Canada.

There are natural gas reserves in Russia, Iran, Venezuela, Qatar, the United States, Saudi Arabia and the United Arab Emirates, among others.

Physical and chemical properties

Among the properties of carbon we can mention the following:

Chemical symbol

C.

Atomic number

6.

Physical state

Solid, under normal pressure and temperature conditions (1 atmosphere and 25 ^° C).

Color

Gray (graphite) and transparent (diamond).

Atomic mass

12.011 g / mol.

Melting point

500 ^° C.

Boiling point

827 ^° C.

Density

2.62 g / cm ³.

Solubility

Insoluble in water, soluble in CCl ₄ carbon tetrachloride.

Electronic configuration

1s ² 2s ² 2p ².

Number of electrons in the outer or valence shell

Four.

Link capacity

Four.

Catenation

It has the ability to form chemical compounds in long chains.

Biogeochemical cycle

The carbon cycle is a biogeochemical circular process through which carbon can be exchanged between the Earth's biosphere, atmosphere, hydrosphere, and lithosphere.

The knowledge of this cyclical process of carbon on Earth makes it possible to demonstrate human action on this cycle and its consequences on global climate change.

Carbon can circulate between the oceans and other bodies of water, as well as between the lithosphere, in soil and subsoil, in the atmosphere and in the biosphere. In the atmosphere and hydrosphere, carbon exists in a gaseous form as CO ₂ (carbon dioxide).

Photosynthesis

Carbon from the atmosphere is captured by terrestrial and aquatic producing organisms in ecosystems (photosynthetic organisms).

Photosynthesis allows a chemical reaction to occur between CO ₂ and water, mediated by solar energy and chlorophyll from plants, to produce carbohydrates or sugars. This process transforms simple molecules with low energy content of CO ₂, H ₂ O and oxygen O ₂, into complex high-energy molecular forms, which are sugars.

Heterotrophic organisms - which cannot photosynthesize and are consumers in ecosystems - obtain carbon and energy by feeding on producers and other consumers.

Respiration and decomposition

Respiration and decomposition are biological processes that release carbon into the environment in the form of CO ₂ or CH ₄ (methane produced in anaerobic decomposition; that is, in the absence of oxygen).

Geological processes

Through geological processes and as a consequence of the passage of time, the carbon from anaerobic decomposition can be transformed into fossil fuels such as oil, natural gas and coal. Likewise, carbon is also part of other minerals and rocks.

Human activity interference

When man uses the burning of fossil fuels for energy, carbon returns to the atmosphere in the form of huge amounts of CO ₂ that cannot be assimilated by the natural biogeochemical carbon cycle.

This excess CO ₂ produced by human activity negatively impacts the balance of the carbon cycle and is the main cause of global warming.

Figure 2. Biogeochemical cycle of carbon. Carbon_cycle-cute_diagram.jpeg: User Kevin Saff on en.wikipedia Derivative work: FischX Translation: Tomás Clarke, via Wikimedia Commons

Applications

The uses of carbon and its compounds are extremely varied. The most prominent with the following:

Oil and natural gas

The main economic use of carbon is represented by its use as a fossil fuel hydrocarbon, such as methane gas and oil.

Oil is distilled in refineries to obtain multiple derivatives such as gasoline, diesel, kerosene, asphalt, lubricants, solvents and others, which in turn are used in the petrochemical industry that produces raw materials for the plastics, fertilizers, drugs and paints industries., among other.

Graphite

Graphite is used in the following actions:

- It is used in the manufacture of pencils, mixed with clays.

- It is part of the elaboration of refractory bricks and crucibles, resistant to heat.

- In various mechanical devices such as washers, bearings, pistons and seals.

- It is an excellent solid lubricant.

- Due to its electrical conductivity and its chemical inertness, it is used in the manufacture of electrodes, carbons for electric motors.

- It is used as a moderator in nuclear power plants.

Diamond

Diamond has particularly exceptional physical properties, such as the highest degree of hardness and thermal conductivity known to date.

These characteristics allow industrial applications in tools used to make cuts and instruments for polishing due to their high abrasiveness.

Its optical properties - such as transparency and the ability to break down white light and refract light - give it many applications in optical instruments, such as in the manufacture of lenses and prisms.

The characteristic luster derived from its optical properties is also highly valued in the jewelry industry.

Anthracite

Anthracite is difficult to ignite, it is slow-burning and requires a lot of oxygen. Its combustion produces little pale blue flame and emits a lot of heat.

Some years ago, anthracite was used in thermoelectric plants and for domestic heating. Its use has advantages such as the production of little ash or dust, little smoke and a slow combustion process.

Due to its high economic cost and its scarcity, anthracite has been replaced by natural gas in thermoelectric plants and by electricity in homes.

Coal

Coal is used as raw material to obtain:

- Coke, fuel from blast furnaces in steel mills.

- Creosote, obtained by mixing the tar distillates from coal and used as a protective sealant for wood exposed to the elements.

- Cresol (chemically methylphenol) extracted from coal and used as a disinfectant and antiseptic, - Other derivatives such as gas, tar or pitch, and compounds used in the manufacture of perfumes, insecticides, plastics, paints, tires and road pavements, among others.

Lignite

Lignite represents a medium quality fuel. Jet, a variety of lignite, is characterized by being very compact due to the long carbonization process and high pressures, and is used in jewelry and ornamentation.

Peat

Peat is used in the following activities;

- For the growth, support and transport of plant species.

- As organic compost.

- As an animal bed in stables.

- As a low quality fuel.

References

1. Burrows, A., Holman, J., Parsons, A., Pilling, G. and Price, G. (2017). Chemistry3: Introducing Inorganic, Organic and Physical Chemistry. Oxford University Press.
2. Deming, A. (2010). King of the elements? Nanotechnology. 21 (30): 300201. doi: 10.1088
3. Dienwiebel, M., Verhoeven, G., Pradeep, N., Frenken, J., Heimberg, J. and Zandbergen, H. (2004). Superlubricity of Graphite. Physical Review Letters. 92 (12): 126101. doi: 10.1103
4. Irifune, T., Kurio, A., Sakamoto, S., Inoue, T. and Sumiya, H. (2003). Materials: Ultrahard polycrystalline diamond from graphite. Nature. 421 (6923): 599–600. doi: 10.1038
5. Savvatimskiy, A. (2005). Measurements of the melting point of graphite and the properties of liquid carbon (a review for 1963–2003). Coal. 43 (6): 1115. doi: 10.1016