CBSE Notes Class 10 Science Chapter 4 - Carbon and its Compounds

1.0Unique Properties of Carbon

Carbon stands out in the periodic table due to its remarkable ability to form a diverse range of compounds. This is mainly because of two unique properties:

1. Catenation: Carbon can bond with other carbon atoms to form varied structures such as chains, branches, and rings, leading to numerous saturated and unsaturated compounds.
2. Valency of Four: Carbon’s four valency allows it to bond with up to four other atoms, resulting in compounds with a wide range of properties. Its small size contributes to the strength and stability of these bonds.

Carbon is a versatile element that forms the basis for all living organisms and many of the materials we use. It can form covalent bonds with itself and other elements to create a multitude of compounds with various properties.

2.0Bonding in Carbon

Carbon predominantly forms covalent bonds and can catenate, or form long chains and rings by bonding to itself. It usually forms single, double, or triple bonds and can combine with other elements like hydrogen, oxygen, nitrogen, sulfur, and halogens.

• Low Melting and Boiling Points: Carbon compounds are characterized by low melting and boiling points due to weak intermolecular forces.
• Poor Electrical Conductivity: These compounds do not conduct electricity well because they do not form ions.

3.0Formation of Covalent Bonds

• Carbon, with four valence electrons, forms stable covalent bonds rather than ionic bonds. It shares electrons with other atoms to achieve a full outer electron shell, forming structures like chains, rings, or branched molecules.

Properties Resulting from Covalent Bonds

• The strong covalent bonds within molecules and weak forces between them explain the physical properties of carbon compounds such as low melting points and electrical non-conductivity.

4.0Allotropes of Carbon

Carbon exists in several allotropes, including diamond (hard and transparent), graphite (soft and opaque, a good conductor of electricity), and amorphous forms like coal and charcoal. Recent discoveries like fullerenes and graphene are also notable for their unique properties. Here are some important allotropes of carbons-

Diamond: Strong covalent bonds create a hard, transparent structure, ideal for industrial cutting and jewelry.

Graphite: Layers of carbon atoms bonded in a hexagonal lattice make it soft, slippery, and electrically conductive.

Fullerenes: Spherical structures like C₆₀ are useful in scientific research due to their unique geometry.

Graphene: A single layer of carbon atoms known for its incredible strength and conductivity, promising for high-tech applications.

Carbon Nanotubes: Cylindrical rolled-up graphene sheets noted for their strength and electrical properties, useful in nanotechnology.

5.0Hydrocarbons

Hydrocarbons are compounds composed solely of carbon and hydrogen. They can be classified as:

• Saturated Hydrocarbons (Alkanes): Contain single bonds between carbon atoms and are generally less reactive.
• Unsaturated Hydrocarbons:
• • Alkenes: Contain one or more double bonds and are more reactive than alkanes.
  • Alkynes: Contain one or more triple bonds and are even more reactive.

6.0Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. Common functional groups include hydroxyl (-OH), carboxyl (-COOH), and amino (-NH₂) groups.

Homologous Series

• A homologous series is a series of compounds with the same functional group, differing by CH₂ units. This series shows gradual changes in physical properties and a pattern in their chemical reactivity.

Nomenclature of Carbon Compounds

• The naming of organic compounds follows specific rules set by the IUPAC. The name reflects the number of carbon atoms, the type of carbon bonds, and the functional groups present in the compound.

 Rules for Carbon Compound Nomenclature:

The nomenclature of carbon compounds follows a systematic approach:

1. Base Name: Identify the number of carbon atoms to determine the base name (e.g., "propane" for three carbons).
2. Functional Groups: Add prefixes or suffixes to indicate functional groups. Remove the final 'e' from the base name if the suffix starts with a vowel (e.g., "propanone" for a ketone).
3. Unsaturation: Change the ending from 'ane' to 'ene' for double bonds and 'yne' for triple bonds (e.g., "propene" for a double bond, "propyne" for a triple bond). This ensures clarity in identifying the structure and characteristics of the compound.

Here’s a table with examples to illustrate the naming of various types of carbon compounds:

7.0Chemical Properties of Carbon Compounds

• Combustion: Carbon compounds burn in oxygen to give carbon dioxide, water, heat, and light.

CH_4​ + 2O₂​ → CO₂​ + 2H₂​O + heat + light.

• Oxidation: Reacts with oxygen or oxidizing agents, often forming alcohols, ketones, or carboxylic acids.

CH₃​CH₂​OH + [O] → CH₃​COOH

• Addition Reaction: Typical of unsaturated hydrocarbons where atoms add to the carbon atoms of a double or triple bond.

C_2​H_4​ + H₂ ​→ C₂​H₆

• Substitution Reaction: Characteristic of saturated hydrocarbons where an atom or group of atoms replaces another.

CH₄​ + Cl_2​ → CH₃​Cl + HCl

8.0Important Compounds of Carbon

Ethanol and Ethanoic Acid

• These are two carbon-based compounds with significant uses. Ethanol is commonly used as a beverage, solvent, and in fuels. Ethanoic acid (vinegar) is widely used in food preparation and as a preservative.

Soaps and Detergents

• Soaps are sodium or potassium salts of long-chain fatty acids, used in cleaning and as emulsifying agents. Detergents are similar but are generally more soluble in hard water and can be made from petroleum products.