Carbon: Properties, Bonding, Characteristics, Structure and Functions

Carbon is extremely versatile because of its ability to chemically combine with itself as well as many other elements in the periodic table. 18 percent of all the matter in living organisms are formed by carbon compounds. Tetra-valence of carbon, saturated and unsaturated carbon compounds, the nomenclature of carbon compounds and their physical and chemical properties are some of the fundamental topics that will help understand the element better.

Read More: Saturated Hydrocarbons

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Properties of Carbon

Carbon is a non-metallic element which occurs in various forms and has very diverse chemical properties. A carbon atom can easily share its four valence electrons with the valence electron of another atom not necessarily of the same kind. By doing so C atom attains octet and hence forms a stable compound. 

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Chemical Properties of Carbon

Here are the two most important properties of carbon:

• Catenation: One carbon atom can form a bond with up to four other carbon atoms. When carbon atoms form long chains using single, double or triple covalent bonds, it is called catenation. Out of all elements, catenation is extensively found in C atoms. Due to this property, carbon is capable of forming an uncountable number of useful chemical compounds.
• Tetra-Valent: There are four electrons in the outermost shell of a carbon atom. This enables the C atom to form a variety of bonds with hydrogen, oxygen, nitrogen, halogens and many other elements. The carbon atom is also relatively small in size, which allows the bond it forms with similar-sized atoms to be exceptionally strong and stable. 

Physical Properties of Carbon

Carbon is a non-metallic element which occurs in various forms. Some of the important physical properties of carbon are given below.

• Usually it is soft, dull and grey in colour. Diamond is an exceptional form of carbon which is the hardest substance present and is rather very bright when optically designed.
• Carbon has a number of allotropes which have different physical as well as chemical properties.
• Carbon can conduct electricity in the form of graphite. 

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Bonding in Carbon

Carbon could either donate or gain 4 electrons to attain its octet. However, due to the small size of carbon, the nuclear force exerted on the outer electron is high and hence, complete transfer of electrons is not feasible. There comes the concept of sharing. Instead of giving away or taking 4 electrons to or from another atom, carbon shares its valence electrons with the valence electrons of the bonding atom. This type of chemical bonding is termed as a covalent bond. As a result both the atoms attain their nearest stable electronic configuration giving rise to a molecule. 

For instance, the H atom in the figure has an unpaired valence electron and C atom has 4 valence electrons. H and C share their valence electrons to make a shared pair. This is called a single bond. The H atom now has 2 electrons in its valence shell and the electronic configuration of stable Helium atoms. Whereas, C has to share all of its valence electrons with four different H atoms to attain its nearest stable configuration.

Carbon Bonding

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Characteristics of Carbon

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Carbon Compounds: Saturated and Unsaturated

When carbon forms covalent bonds with one or more hydrogen atoms, the compound formed is called a hydrocarbon. Hydrocarbons can be classified into two categories on the basis of the type of bonding between the carbon atoms. Saturated hydrocarbons are those that have C-C single covalent bond(s). Unsaturated hydrocarbons possess one or multiple double or triple bonds between carbon atoms. Methane, ethane, propane, butane and so on are saturated hydrocarbons where ethene, propene and ethyne etc are unsaturated hydrocarbons with double and triple covalent bonds.

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Nomenclature of Carbon Compounds

The existence of a large number of hydrocarbons makes it impossible to use trivial names for each compound. To make it easier to remember the names of hydrocarbons a special convention was devised to determine the names. This conventional naming of hydrocarbons is called nomenclature.

Read More: Lewis Dot Structure

Steps to Name a Hydrocarbon:

• Begin with the number of carbon atoms in the hydrocarbon. The name of a compound depends on how many carbon atoms it has. For example : CH₄ having one carbon is called Methane whereas C₂H₆ with 2 carbon atoms is called Ethane. 

• Once the number of carbon atoms is determined, check if there is any functional group present. A functional group requires either prefix or a suffix in the name of the hydrocarbon. If the name of a functional group is a suffix and begins with a vowel a, e, I, o or u, then the ending ‘e’ from the name of the carbon chain is removed and the suffix is fixed at its place. 

For example, CH₃OH is named as Methane - ‘e’ + ‘ol’ = Methanol

• The name of a saturated hydrocarbon ends with ‘ane’ while that of unsaturated hydrocarbon ends with ‘ene’ or ‘yne’ for double and triple bonds respectively.

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Important Carbon Compounds

Ethanol

Chemical Formula: C₂H₅OH

Characteristics: 

• Liquid at room temperature
• Commonly called as alcohol and used in alcoholic drinks
• Is a good solvent and used for medicinal purposes.

Reactions:

• When ethanol reacts with sodium ethoxide is formed.
  2Na + 2CH₃CH₂OH → 2CH₃CH₂O–Na⁺ + H₂ (Sodium ethoxide)
• On heating ethanol at 443K in presence of excess conc. sulphuric acid, ethene is formed.
  CH₃ −CH₂OH CH₂ = CH₂ + H₂O

Read More: Carbocation Stability

Ethanoic Acid

Chemical Formula: CH₃COOH

Characteristics: 

• Commonly called as acetic acid
• Solution of acetic acid (5-8%) is called vinegar
• Used as preservative for food items

Reactions: 

• When ethnic acid reacts with ethanol a compound called ester having a very pleasant smell is formed and the reaction is called an esterification reaction.
• When ethanoic acid reacts with a base they form salt and water. The salt is commonly called acetate.
  NaOH + CH₃COOH → CH₃COONa + H₂O

                                          (Sodium Acetate)

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Function and Application of Carbon

Carbon finds its uncountable usage in human life. However it is as important to every life form possible. Below are a few of the many useful functions and applications of carbon.

• Clay along with carbon in its allotropic form of graphite is used to make pencil lead. Graphite is a great lubricant used in machinery. Graphite is used as electrodes in dry batteries for various electrolytic processes.
• Carbon forms a major content in cellulose which is the polymer which forms wood, cotton etc. 
• Coal is of immense value in developing countries like India. Coal is directly and indirectly used as fuel or production of other fuels.
• Diamond which is an allotrope of carbon is one of the most valued gems. Diamond is extremely hard which makes it useful in industrial purposes like cutting glass and other hard substances too.
• Hydrocarbons like methane are very important fossil fuels. Carbon compounds also make a large part of the crude oil.

Read More: Collision Theory

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Things to Remember

• Carbon is one of the most abundant elements in the universe. Carbon contributes to a large variety of compounds due to its tetravalency and catenation property. There are nearly ten million known carbon compounds. We use a large number of carbon compounds in our essential daily activities.
• Diamond and graphite are two allotropes of carbon. This means that they are made up of carbon atoms , however the bonding between the carbon atoms in each form is different. Graphite is a conductor of electricity. Diamond is the hardest substance known.
• Soaps are potassium and sodium salt of fatty acids. A soap molecule has two ends. The hydrocarbon chain end is hydrophobic whereas the end containing the metal ion is hydrophilic. This enables soap to form micelles which helps in cleaning dirt and grease.

Read More: Properties Of Bases