Why Carbon 12 is Taken as Standard || Why Carbon is Important

11 min readAug 6, 2019

Carbon is a non-metallic element located in Group IVA of the second cycle of the Periodic Table of the Elements. Latin is Carbonium, which means “ coal, charcoal”. Carbon 12 is a very common element that is found in many forms in the atmosphere and in the earth’s crust and living things.

The carbon element has been recognized and utilized very early, and a series of carbon compounds, organic matter, are the foundation of life. Carbon is one of the components of pig iron, wrought iron, and steel. Carbon can chemically self-bond to form a large number of compounds, biologically and commercially important molecules. Most molecules in the organism contain carbon.

Discovery History of Carbon

The English name of carbon is derived from the name of carbo in Latin coal and charcoal. It is also derived from the charbon in French, which means charcoal.

In Germany, the Netherlands and Denmark, the names of carbon are Kohlenstoff, koolstof, kulstof, which literally means coal.

Carbon has been discovered in prehistoric times, and carbon black and coal are the first forms of carbon used by humans.

Diamonds were known to China around 2500 BC, and coal was used in the form of carbon in the Roman era in the same way as modern times: the air was removed by heating clay-covered wood in a vertebral building.

In 1722, René Antoine Ferchault de Réaumur proved that iron can be converted into steel by absorbing some substances, which is now known as carbon. In 1772, Anthony Lavoisier showed that diamonds are a form of carbon.

When he burns samples of diamonds and coal, they find that they do not produce water and that each gram of diamonds and coal is produced.

The amount of carbon dioxide is equal. In 1779, Carl Wilhelm Scheele showed that once thought to be present in the form of lead — Graphite is essentially a mixture of carbon mix a small amount of iron, and he gave when the nitric acid oxidation, product name air Acid (“ aerial acid “), that is, carbon dioxide.

In 1786, French chemists Claude Louis Berthollet, Gaspard Monge and CA Vandermonde oxidized graphite by using Lavoisier to treat diamonds, demonstrating that graphite consists almost entirely of carbon. In1789, Lavoisier listed carbon in the element table in his textbook.

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Existence Distribution

Mineral form

Carbon exists in the form of free elements ( diamond, graphite, etc.) and in the form of compounds (mainly carbonates of calcium, magnesium and other electropositive elements).

It exists in the form of carbon dioxide and is a small but extremely important component of the atmosphere. The total abundance of carbon in crust rocks is expected to vary considerably, but the typical value can be 180 ppm, in abundance order, this element is in the 17th position, after yttrium, lanthanum, sulfur, before zirconium, vanadium, chlorine, chromium.

Graphite is widely distributed throughout the world, but most have little value. A large number of crystals or flakes are present in denatured sedimentary silicate rocks such as quartz, mica, schist, and gneiss; crystal sizes range from less than 1 mm to about 6 mm (average 4 mm).

It deposits a micro-lentil-like ore body that can reach up to 30m thick and crosses the field for several kilometers. The average carbon 12 content is 25%, but the high is 60% (Margash).

The beneficiation is carried out by treatment with hydrofluoric acid and hydrochloric acid and then heated to 1500 °C in a vacuum.

Microcrystalline graphite (sometimes referred to as “amorphous”) is present in carbon-rich denatured precipitates, and some Mexican deposits contain up to 95% carbon.

Diamond is a tubular igneous conglomerate (volcanic volcano) from an ancient volcano embedded in a soft, dark, alkaline rock called “blue soil” or “lithite-bearing igneous rock”, South Africa, 1870 The city of Jim Burley found such a volcano for the first time.

With the change of geological age, diamonds can be found in the scouring gravel and on the beach by weathering corrosion of the volcanic canister. The original mode of forming diamond crystals is still a subject of active research.

The diamond content of a typical diamond-containing volcanic cylinder is extremely low, on the order of one-millionth.

The mineral must be separated by mechanical means such as pulverization and panning and passed through the greased belt. The diamond will stick to it. This explains to some extent the reason why gem-quality diamonds are extremely expensive.

Three other forms of carbon are manufactured on a large scale and widely used in industry: they are coke, carbon black and activated carbon.

Cycle in Nature

Underground conditions, it is rare for an element to go from one place to another. Therefore, the carbon content on the earth is an effective constant. The flow of carbon in nature constitutes the carbon cycle.

For example, plants absorb carbon dioxide from the environment to store biomass energy, such as carbon respiration and the Calvin cycle (a process of carbon fixation). Some biomass can be transferred by predation, while some carbon is exhaled by animals in the form of carbon dioxide.

The structure of the carbon cycle is much more complicated than the pattern diagram on the right. For example, some carbon dioxide can dissolve in the ocean, and the remains of dead plants or animals can form coal, oil, and natural gas, which can be burned to release carbon, which is not available to bacteria.

Formation in Stars

The formation of carbon nuclei requires almost simultaneous triple collisions of alpha particles (deuterons) in giant nuclei or supergiants. This process is called the three-pronged process.

This nuclear fusion reaction can occur rapidly within the high temperature and enthalpy-rich stars of more than 100 million K.

Similarly, he occurs in older ages, and helium accumulated through the proton-proton chain reaction and the carbon-nitrogen cycle, accumulating in the core stars.

After the core hydrogen has burned, the core will collapse until the temperature reaches the ignition point of the helium. The process of reaction is:

4He+ 4He→ 8Be (−93.7 keV) 8Be+ 4He→ 12C (+7.367 MeV)

The net energy released from the reaction was 1.166 pJ.

Another fusion mechanism for star energy supply is the CNO cycle ( carbon-nitrogen-oxygen cycle, sometimes referred to as the bass-Weizzek-cycle, which is one of two processes in which a star converts hydrogen into helium, and the other the process is a proton-proton chain reaction) in which carbon acts as a catalyst to enable the reaction to proceed.

Physical properties

Carbon Isotopes

There are fifteen species of isotopes known in modern times, with carbon 8 to carbon 22, of which carbon 12 and carbon 13 are stable, and the rest are radioactive, with carbon 14 having a half-life of 5730 years and others being stable isotopes.

In the natural world of the Earth, carbon 12 accounts for 98.93% of all carbon and 1.07% of carbon-13. The atomic weight of C is the weighted average of the carbon 12 and 13 isotope weights, which is generally 12.01.

Carbon 12 is a standard for defining moles in the International System of Units, and the number of atoms contained in 12 grams of carbon 12 is 1 mole.

Carbon 14 has a long half-life, decay mode is beta decay, carbon 14 atom is converted into nitrogen atom and carbon is one of the elements of organic matter.

When living, the carbon 14 content in the body is roughly unchanged due to the need to breathe. After the creature dies, it will stop breathing, and the carbon 14 in the body begins to decrease.

One can estimate its approximate age by measuring the carbon 14 content of an antiquities. This method is called the carbon dating method.

Allotrope

Diamond Carbon

Naturally, in the form of anthracite (a type of coal), graphite and diamonds, it has historically been easier to obtain coal ash or charcoal.

Ultimately these different materials are considered to be formed from the same elements. Not surprisingly, diamonds are the hardest to identify.

The naturalist Giuseppe Averani from Florence (Italy) and the medical scientist Cipriano Targioni first discovered that diamonds can be destroyed by heat.

In 1694 they used a large magnifying glass to gather sunlight onto the diamonds, and the gem eventually disappeared. Pierre-Joseph Macquer and Godefroy de Villetaneuse repeated this experiment in 1771.

Then, in 1796, the British chemist Smithson Tennant showed that only CO 2 was produced after combustion and finally proved that diamond is only a form of carbon.

Diamond is the most solid carbon structure in which carbon atoms are arranged in the form of a crystal structure. Each carbon atom is tightly bonded to four other carbon atoms to form a spatial network structure, which ultimately forms a hardness and activity. carbon 12

Diamond has a high melting point and a melting point of over 3500°C, which is equivalent to some stellar surface temperatures.

In a diamond molecule, each carbon atom is surrounded by four other carbon atoms. These carbon atoms are joined together by a strong bonding force to form a huge molecule, so the diamond is very hard. Diamond is an insulator. The purpose is to make decorations, drill materials, etc.

Graphite is a shiny dark gray metallic opaque sweetlips flaky solid. Graphite is a mixed crystal that has both the properties of atomic crystals and the properties of molecular crystals.

It is soft, has a slippery feel and has excellent electrical conductivity. The melting point is high. Each carbon atom in the graphite molecule combines with only three other carbon atoms with a strong force to form a layered structure, and the bonding force between the layers is small, so graphite can be used as a lubricant. The purpose is to make pencils, electrodes, tram cables, etc.

Pyrophyllite (when Chaoite, meteorite collision with graphite, the atoms are arranged in a hexagonal pattern)

Mercury antimony structure (Schwarzite, due to the appearance of a heptagon, the hexagonal layer is twisted to the hypothetical structure in the “negative curvature” saddle shape) carbon fiber (Filamentous carbon, a small pile of fibers formed by the growth chain)

Carbon aerogels (very small density porous structures similar to well-known silicon aerogels)

Carbon nanofoam (Carbon nanofoam, spider, with the fractal structure, a density of one percent of carbon airgel, ferromagnetic).

Graphene is a two-dimensional crystal, in which the characteristics of the maximum electron velocity reaches the speed of light to 1/300, far exceeding the speed of electrons moving in the general conductor.

This makes the properties of electrons in graphene, or more accurately, what should be called “electric charge carriers”, very similar to relativistic neutrinos.

The common graphite is formed by stacking a layer of planar carbon atoms arranged in a honeycomb order.

The interlayer force of graphite is weak, and it is easy to peel off each other to form a thin graphite sheet. When the graphite sheet is peeled off into a single layer, the single-layer having only one carbon atom thickness is graphene. carbon 12

Other configurations amorphous carbon (Amorphous, not really shaped body, the internal structure of graphite)

Chemical Properties

Simple substance

Burning in oxygen

Vigorously exothermic, giving off glare white light, producing a colorless and odorless gas that makes the calcium hydroxide solution (clear lime water) turbid.
Chemical equation:
C+O 2 == ignition== CO 2 (combination reaction)

Combustion in the air,
exothermic, continuous red heat, producing a gas CO 2 that is colorless and odorless to make the calcium hydroxide solution (clear lime water) turbid when the combustion is insufficient, that is, when the amount of oxygen is insufficient, carbon monoxide is generated:
sufficient oxygen Chemical equation:
C+O 2 == ignition== CO 2 (combination reaction)

Chemical equation when oxygen is insufficient:
2C+O 2 == ignition== 2CO (combination reaction)

As a reducing agent,
carbon as a reducing agent possesses chemical properties similar to hydrogen and carbon monoxide (but different in production), and metal elements can be reduced from metal oxides.
Carbon reduction copper oxide:
C+2CuO== high temperature==2Cu+CO 2 ↑ (displacement reaction)
carbon reduction iron oxide:
3C+2Fe 2 O 3 == high temperature==4Fe+3CO 2 ↑ (displacement reaction)
carbon reduction carbon dioxide:
C+CO 2 == High temperature== 2CO (combination reaction)
However, carbon is co-heated in the sealed space with potassium permanganate. Potassium permanganate decomposes oxygen, and carbon will oxidize rapidly and will explode. carbon 12

Reacts with strong oxidizing acids:

C+2H2SO4 (concentrated) == heating == CO2 ↑ + 2SO2 ↑ + 2H2O C+4HNO3 (concentrated) == heating == CO2 ↑ 4NO2 ↑ + 2H2O

Stability
Carbon has stability under “normal temperature” and is not easy to react. Therefore, ancient famous paintings can be preserved in modern times, and carbon inks are required for writing files.

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Carbon Compound

Carbon compounds, only inorganic compounds belonging to the following: carbon oxides, carbides, carbon-chalcogen compound, carbon disulfide (the CS 2), carbonate, bicarbonate, cyanide, and a series of quasi halo and quasi halogenated Compounds , pseudohalides, such as cyanide [(CN) 2], oxycyanide [(OCN) 2], thiocyanate [(SCN) 2], other carbon-containing compounds are organic compounds.

Since the bonds formed by carbon atoms are relatively stable, the number, arrangement, and type and position of carbon in the organic compound are highly random, thus causing an extremely large number of organic substances, which are found in modern human compounds.

Organic matter accounts for the vast majority. The nature of organic matter is very different from that of inorganic substances. They are generally flammable, not easily soluble in water, and have a complex reaction mechanism. They have formed an independent sub-division, organic chemistry.

Toxicological Properties

Pure carbon is extremely low in toxicity to humans and can be processed and even safely ingested in the form of graphite or activated carbon. Carbon can resist dissolution or chemical attack, for example, even in the face of acidic substances in the digestive tract.

Therefore, once it enters human tissue, it may remain indefinitely. Carbon black is probably one of the first pigments used in tattoos. For example, Ice Man Oz was found to have carbon black tattoos. These tattoos have existed since his survival until 5200 years after his death. carbon 12

However, inhalation of large amounts of coal (or carbon black) dust or fumes are dangerous, they can stimulate lung tissue and cause congestion pneumoconiosis. Similarly, diamond grinding can be dangerous if it is eaten or inhaled.

carbon 12 is low-toxic to almost all living things on Earth, but it is toxic to certain organisms. For example, carbon nanoparticles are fatal to fruit flies. carbon range of compound types, both lethal toxins such as tetrodotoxin, from castor extracted seeds ricin, cyanide and carbon monoxide, are also essential for life species such as glucose, protein.

Preparation Method

Diamond

The diamond supply chain is controlled by a limited trading group in a limited number and is highly concentrated in a small area of the world. Only a very small amount of mineral deposits have practical value.

Care must be taken during the comminution of the ore to prevent damage to the diamond during this process and then order the diamonds in order of density.

The final sorting step in the process is done by hand before the diamond is graded according to the enrichment density by means of X-rays.

Before it became commonplace with X-ray operation, the separation was done with a greased belt that was more adhesive than other minerals.

Graphite

Commercially valuable graphite deposits are found all over the world, but the most important economic sources are in China, India, Brazil, and North Korea.

The graphite deposits in Borrowdale, Cumberland, England were first of sufficient size and purity. Before the 19th century, pencils were simply wrapped with natural graphite saw blades.

After the 21st century, small graphite deposits were obtained by pulverizing the parent rock and allowing the lightweight graphite to float out of the water.