We explain what carbon is, why this element is so important for life and what its main characteristics are.
What is the carbon atom?
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 the combustion process as it forms part of carbon dioxide (CO2).
Carbon It occurs under numerous structures and also in an amorphous manner; its physical properties are often very contrasting. It has the property of being able to combine with almost all elements; it can combine with both metals and non-metals (examples: calcium carbide (CaC2), carbon disulfide (CS2), chloroform (CHCl3), etc.).
They are estimated approximately about 10 million carbon compoundsmany of them essential for life on the planet.
See also: Organic chemistry
Characteristics of the carbon atom
- 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 its 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 1s22s22p2.
- It is tetravalent. This means that it has 4 electrons orbiting in its final energy level, which can combine with the outermost electrons of other atoms, often also carbon, forming covalent bonds. This means that carbon can form four chemical bonds.
- Presents allotropyIt can be present in 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.
- Has isotopesCarbon has only two natural isotopes: carbon-12, which is the majority (98.90%), and carbon-13, which is present in minimal proportion (1.10%). In addition, there are thirteen unstable isotopes with half-lives ranging from 200 nanoseconds (as in carbon-22) to 5,730 years (as in carbon-14). Carbon-13 is used in structural studies (especially NMR/Nuclear Magnetic Resonance), and carbon-14 is used to date archaeological objects, given its very long half-life.
- Combines easily. Carbon can combine with both metals and non-metals (for example: calcium carbide (CaC2), carbon disulfide (CS2), chloroform (CHCl3), etc.). It is estimated that there are about 10 million carbon compounds, many of them essential for life.
Carbon hybridizations
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 in the outermost shell can combine with the electrons of other atoms, thus, the carbon atom can form three types of hybridizationswhich have implications for the final molecular geometry of the compounds formed by carbon. These hybridizations can be:
- sp3 hybridization. Explains the formation and geometry of compounds with single bonds, which have a tetrahedron-shaped geometry.
- sp2 hybridization. Explains the formation and geometry of compounds with double bonds, which can have planar trigonal geometry.
- sp hybridization. Explains the formation and geometry of compounds with triple bonds, which have linear geometry.
Three possible configurations
Given the the type of union (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 single 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°.
Reactivity of carbon
- Compounds formed by 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’s fuel.
- Carbon reacts with oxygen to form primarily carbon dioxide (CO2) and carbon monoxide (CO).
Relative similarity to silicon
Carbon is the first member of group IVA within the Periodic Table of elements. Next in this group is silicon (Si), which also has 4 electrons in its outermost shell, but at a higher energy level.
However, silicon cannot form multiple silicon-silicon bonds due to the repulsion generated by a greater number of internal electrons, which means that the atoms cannot get close enough to each other. Furthermore, both elements are non-metals and are solids at room temperature.
Kekulé and the foundations of organic chemistry
In 1858, the German chemist August Kekulé proposed a structural theory that explained 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 arranged in a cycle and the bonds between them alternate between single and double. This It was fundamental as a precursor to the concept of covalent bonding. introduced by Lewis, which serves as a basis for understanding carbon chemistry in general.
Continue with: Alkenes
References:
- “Carbon Chemistry” Dr. Pedro Ambielle. Buenos Aires. 1937.
- “The Chemical Elements of Life” Frieden, Earl. Scientific American.1972.
- “Carbon” on Wikipedia.
- “The Structural Characterization of Kekulé Benzene: an Example of Creativity and Heuristics in the Construction of Chemical Knowledge” Jorge Meinguer Ledesma. Scielo Editorial. 2020.