Bonds in Carbon Compounds

Carbon is a fundamental element present in all living organisms and many non-living substances. Organic compounds contain carbon, except for a few inorganic carbon compounds like carbonates, bicarbonates, and oxides of carbon.

• Atomic number: 6
• Atomic mass: 12.01 g/mol
• Found in both free (coal, graphite) and combined states (carbonates, hydrocarbons, CO₂).
• Forms bonds with elements like hydrogen, oxygen, chlorine, and sulphur, creating various compounds.

Catenation Property of Carbon:

Carbon has a unique ability to form long chains and rings by bonding with itself. This property is called catenation. Additionally, carbon can form double and triple bonds with elements like oxygen and nitrogen, leading to diverse organic compounds.

Allotropes of Carbon:

Carbon exists in multiple forms called allotropes, which have different physical properties but similar chemical behaviour.

Diamond: the hardest known material, used in jewellery and cutting tools.
Graphite: a good conductor of electricity, used in pencils and lubricants.
Graphene: a single-layer structure with high electrical conductivity.
Fullerenes (C₆₀): spherical molecules used in nanotechnology.
Carbon nanotubes: cylindrical structures with high strength and conductivity.

Ionic compounds have high melting and boiling points and conduct electricity in molten and dissolved states due to ionic bonds. In contrast, carbon compounds generally have lower melting and boiling points, as shown in the table below, indicating weaker intermolecular forces.

Most carbon compounds do not conduct electricity, which suggests they lack ionic bonds and do not produce ions in solution.

Electronic Configuration of Carbon

• Atomic number: 6
• Electronic configuration: 2,4
• Valence electrons: 4
• Nearest noble gases: Helium (2), Neon (2,8)

Since carbon has four valence electrons, it can bond in three possible ways to achieve stability:

1. Losing four electrons to form C⁴⁺

• This would require excessive energy, making it unstable.

2. Gaining four electrons to form C⁴⁻

• The carbon nucleus would struggle to hold ten electrons, making this unstable.

3. Sharing four electrons with other atoms (Preferred method)

• Carbon forms covalent bonds, where atoms share electrons instead of transferring them.

Types of Carbon-Based Compounds

1. Hydrocarbons: carbon and hydrogen compounds (e.g., methane CH₄, ethane C₂H₆).
2. Carbon-Oxygen Compounds: Includes CO₂, CO, and CO₃.
3. Carbon-Sulphur Compounds: Examples include CS₂ and OCS.
4. Carbon-Nitrogen Compounds: Includes Cyanogen (CN)₂ and Hydrogen Cyanide (HCN).
5. Carbon-Halide Compounds: Examples: carbon tetrachloride (CCl₄), carbon tetrafluoride (CF₄).

Uses of Carbon and Its Compounds

• Life’s building block: essential for all living organisms.
• Fuels: Hydrocarbons are the primary energy source.
• Polymers: Used in plastics like polyethylene and polypropylene.
• Dyes and drugs: Carbon compounds are used in pharmaceuticals.
• Diamond: Used in jewellery and industrial cutting tools.
• Graphite: Used in pencils, lubricants, and electrodes.
• Glucose: A vital energy source for living cells.

A covalent bond forms when atoms share electrons to complete their valence shells, making them stable without forming ions. The electron-dot structure represents these shared electrons.

Examples of Covalent Bonding:

1. Hydrogen (H₂)

• Each hydrogen atom has one electron and needs one more to be stable.
• Two hydrogen atoms share electrons, forming a single bond (H—H).

Electron dot structure and line structure of hydrogen molecule with a single bond

2. Oxygen (O₂)

• Each oxygen atom has six valence electrons and needs two more.
• Two oxygen atoms share two pairs of electrons, forming a double bond (O=O).

Double Bond

3. Nitrogen (N₂)

• Each nitrogen atom has five valence electrons and needs three more.
• Two nitrogen atoms share three pairs of electrons, forming a triple bond (N≡N).

Triple Bond

4. Methane (CH₄)

• Carbon needs four electrons to be stable.
• It shares one electron each with four hydrogen atoms, forming four single covalent bonds.
• Thus, covalent bonding allows carbon to form a wide variety of stable compounds.

Electron-dot structure and line structure of methane molecule

Models of methane molecule

All the compounds having carbon as a constituent element are called as organic compounds.

The chemical bond formed by sharing of two valence electrons between the two atoms is called covalent bond.

• Organic compounds are mainly carbon compounds, except CO₂, CO, carbonates, bicarbonates, and carbides, which are inorganic.
• Carbon compounds have low melting and boiling points (generally below 300 °C) due to weak intermolecular forces.
• Most carbon compounds do not conduct electricity, showing the absence of ionic bonds.
• Carbon forms covalent bonds by sharing electrons to achieve a stable noble gas configuration.
• Carbon can form single, double, and triple covalent bonds, allowing the formation of many compounds like CH₄, O₂, and N₂.