Why carbon forms millions of compounds
Carbon has four valence electrons and forms covalent bonds by sharing them, since gaining or losing four electrons is very difficult. It shows catenation, the ability to join with other carbon atoms in long chains, branches and rings, and it can form single, double and triple bonds. Diamond, graphite and fullerene are different forms of pure carbon. Saturated hydrocarbons, alkanes, have only single bonds, while alkenes and alkynes are unsaturated.
A homologous series is a family of compounds with the same functional group in which each member differs from the next by a –CH₂– unit, such as methane, ethane and propane. Functional groups like –OH (alcohol), –CHO (aldehyde), –COOH (carboxylic acid) and halogens decide chemical properties. Ethanol is used as a fuel and solvent, and ethanoic acid is the acid in vinegar. When an acid and alcohol react, they form a sweet-smelling ester. Soaps are sodium salts of long-chain fatty acids that remove grease by forming micelles.
Why it matters
Carbon compounds include fuels like LPG and petrol, plastics, medicines, food and the molecules of life itself. Understanding soaps and detergents explains why soap does not lather well in hard water. Burning carbon fuels releases carbon dioxide, linking this topic to climate change. It is the gateway to organic chemistry in Classes 11 and 12.
Key terms
- Catenation
- The ability of carbon atoms to link with one another to form long chains and rings.
- Homologous series
- A group of organic compounds with the same functional group, differing by a CH₂ unit.
- Functional group
- An atom or group of atoms that gives an organic compound its characteristic properties.
- Micelle
- A cluster of soap molecules with oily tails inward that traps grease in water.