Carbon is a unique element that plays a fundamental role in organic chemistry. Its ability to form a variety of bonds and compounds makes it essential for life. Understanding carbon bonding is crucial for studying its compounds.

4.1.1 Tetravalency of Carbon

Carbon has four valence electrons in its outer shell, which allows it to form four covalent bonds with other atoms. This property is known as tetravalency:

• By sharing its four valence electrons, carbon can achieve a stable electronic configuration similar to noble gases.
• This tetravalency allows carbon to bond with a variety of elements, including hydrogen, oxygen, nitrogen, and other carbon atoms.

4.1.2 Types of Bonding

Carbon can form different types of bonds:

• Covalent Bonds: Carbon primarily forms covalent bonds, where electrons are shared between atoms. For example, in methane (CH₄), one carbon atom shares its electrons with four hydrogen atoms:
• C + 4H → CH₄
• Double Bonds: Carbon can also form double bonds, where two pairs of electrons are shared between atoms. For instance, in ethene (C₂H₄), two carbon atoms share two pairs of electrons:
• C₂H₄ → C=C
• Triple Bonds: Carbon can form triple bonds, sharing three pairs of electrons. An example is ethyne (C₂H₂), where two carbon atoms share three pairs of electrons:
• C₂H₂ → C≡C

4.1.3 Hybridization

Carbon exhibits hybridization, a process that mixes atomic orbitals to form new hybrid orbitals for bonding:

• sp³ Hybridization: In methane, carbon undergoes sp³ hybridization, forming four equivalent sp³ orbitals that arrange themselves in a tetrahedral geometry.
• sp² Hybridization: In ethene, carbon undergoes sp² hybridization, resulting in three sp² orbitals that are arranged in a trigonal planar configuration, leaving one p orbital for the formation of a double bond.
• sp Hybridization: In ethyne, carbon undergoes sp hybridization, forming two sp orbitals arranged linearly, which allows the formation of a triple bond.

4.1.4 Isomerism in Carbon Compounds

The versatility of carbon bonding leads to isomerism, where compounds with the same molecular formula have different structures and properties:

• Structural Isomers: Compounds that differ in the arrangement of atoms. For example, butane (C₄H₁₀) can exist as n-butane and isobutane.
• Geometric Isomers: Occur in compounds with double bonds, where the arrangement of substituents differs. For example, cis and trans isomers of 2-butene.
• Stereoisomers: Isomers that differ in the spatial arrangement of atoms. These include enantiomers, which are mirror images of each other.

4.1.5 Role of Carbon in Organic Compounds

Carbon's bonding capabilities allow it to form a vast array of organic compounds:

• Hydrocarbons: Compounds consisting only of carbon and hydrogen. They can be saturated (alkanes) or unsaturated (alkenes and alkynes).
• Functional Groups: Carbon compounds can contain functional groups that determine their chemical properties. Common functional groups include -OH (hydroxyl), -COOH (carboxyl), and -NH₂ (amino).
• Polymers: Long chains of repeating units (monomers) formed from carbon-based compounds. Examples include plastics, proteins, and carbohydrates.