We explain what carbon is, why this element is so important for life and what its main characteristics are.
What is the carbon atom?
The carbon is one of the most abundant elements on Earth , essential for life . It is the main component of organic matter; it also integrates the final product of the metabolism of most living beings and of the combustion process as it forms part of carbon dioxide (CO 2 ).
Carbon occurs under numerous structures and also in an amorphous manner ; their physical properties are often very contrasting. It has the property of being able to combine with almost all the elements ; It can be combined with both metals and non-metals (examples: calcium carbide (CaC 2 ), carbon disulfide (CS 2 ), chloroform (CHCl 3 ), etc.).
Approximately 10 million carbon compounds are estimated , many of them essential for life on the planet.
Characteristics of the carbon atom
Carbon has 6 protons and 6 neutrons in its nucleus.
- Its atomic number is 6 and its atomic mass is 12 . This means that it has 6 protons and 6 neutrons in its nucleus in its stable configuration, and that the nucleus is surrounded by 6 electrons. These electrons are distributed according to the following electronic configuration: two in their first energy level (which has an s orbital) and four in its second energy level (which has the s and p orbitals), this is represented as 1s 2 2s 2 2p 2 .
- It is tetravelent . This means that it has 4 electrons orbiting at its last energy level, which can combine with the outermost electrons from other atoms , often carbon as well, forming covalent bonds . This means that carbon can form four chemical bonds .
- It presents allotropia . It can occur under different molecular structures, in the same physical state, depending on the conditions of formation. The most important allotropes of carbon are: diamond, graphite, lonsdaleite, fullerene, carbon nanotube, amorphous carbon and graphene.
- It presents isotopes . Carbon has only two natural isotopes: carbon-12, which is the majority (98.90%), and carbon-13, present in a minimal proportion (1.10%). In addition, there are thirteen unstable isotopes whose half-life or half-life ranges from 200 nanoseconds (as in carbon-22) to 5730 years (as in carbon-14). Carbon-13 is used in structural studies (especially NMR / Nuclear Magnetic Resonance), carbon-14 is used to date archaeological objects, given its very long half-life.
- It is easily combined . Carbon can combine with both metals and non-metals (for example: calcium carbide (CaC 2 ), carbon disulfide (CS 2 ), chloroform (CHCl 3 ), etc.). There are an estimated 10 million carbon compounds, many of them essential for life.
Atomic orbitals are the probabilities of finding an electron in a region of space around the atomic nucleus. Hybridization is the interaction between these orbitals, which when superimposed form hybrid orbitals that lead to the formation of different chemical bonds.
In the case of carbon, its four electrons from the outermost shell can combine with electrons from other atoms, thus, the carbon atom can form three types of hybridizations , which have implications for the final molecular geometry of the compounds it forms. carbon. These hybridizations can be:
- Sp 3 hybridization . Explain the formation and geometry of compounds with single bonds, which have a geometry in the shape of a tetrahedron.
- Sp 2 hybridization . Explain the formation and geometry of compounds with double bonds, which can have planar trigonal geometry.
- Hybridization sp . Explain the formation and geometry of triple bonded compounds, which have linear geometry.
Three possible configurations
Since the type of bond (determined by the type of hybridization) determines the bond angle, in turn there are three possible molecular geometries when carbon participates in the formation of a chemical bond:
- The simple bond determines the formation of a tetrahedron, with angles of 109.5 °.
- The double bond determines the formation of a flat triangular structure, with angles of 120 °.
- The triple bond determines the formation of a linear structure, with angles of 180 °.
- Compounds made of carbon that have multiple bonds (double or triple) between carbon atoms are more reactive than those with single bonds.
- Carbon reacts with hydrogen to form hydrocarbons .
- It is fuel.
- Carbon reacts with oxygen to form mainly carbon dioxide (CO 2 ) and carbon monoxide (CO).
Relative similarity to silicon
Carbon is the first member of group IVA within the Periodic Table of the elements. It is followed in this same group by silicon (Si), which also has 4 electrons in its outermost shell, but at a higher energy level.
However, silicon cannot form silicon-silicon multiple bonds because of the repulsion generated by a greater number of internal electrons, which makes the atoms unable to get close enough. On the other hand, both elements are nonmetals and are solid at room temperature.
Kekulé and the foundations of organic chemistry
The German chemist August Kekulé postulated in 1858 a structural theory that allowed to explain the resonance phenomenon of benzene. He proposed that benzene is made up of 6 carbon atoms and 6 hydrogen atoms, but the carbon atoms are organized in the form of a cycle and the bonds between them alternate between single and double. This was fundamental as an antecedent to the concept of covalent bonding introduced by Lewis, which serves as the basis for understanding carbon chemistry in general.
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