RRB Group D 27 Nov 2025 Shift 2 Solved Paper

Concept:The vast number of carbon compounds results from the combined effect of tetravalency (four bonding sites) and catenation (self-linking).Explanation:Carbon has four valence electrons, giving it a tetravalent nature.This allows carbon to form four strong covalent bonds with atoms like $H$, $O$, $N$, and other $C$ atoms.Catenation is the unique ability of carbon to bond with itself to form long chains, branched chains, and rings.These two properties together enable an enormous variety of molecular frameworks.For example, carbon can form single bonds (e.g., $CH_4$), double bonds (e.g., $C_2H_4$), and triple bonds (e.g., $C_2H_2$).Straight chains, branched chains (e.g., isobutane), and cyclic structures (e.g., benzene) are all possible due to catenation.The combination of tetravalency and catenation allows millions of unique organic molecules, including hydrocarbons, alcohols, and acids.Solubility alone is not a characteristic feature of carbon that leads to a large number of compounds.Therefore, both tetravalency and catenation are essential.Answer:Both tetravalency and catenation