Catenation
- CBSE · NCERT Class 10, Ch 4 Carbon and its Compounds
Catenation is the ability of an element's atoms to bond with each other and form long chains, branches or rings.
Carbon atoms join to other carbon atoms very easily. They can form straight chains, branched chains and rings. The links can be single, double or triple bonds. This is why there are millions of carbon compounds.
Carbon has a second feature too. It has a valency of 4, so each carbon can bond with up to 4 other atoms. Catenation and this valency together explain the huge number of carbon compounds.
A small example
Take a chain of 4 carbon atoms: C–C–C–C. Each end carbon uses 1 bond on the chain and has 3 left for hydrogen. Each middle carbon uses 2 and has 2 left. So the chain holds 3 + 2 + 2 + 3 = 10 hydrogen atoms. That is butane, C₄H₁₀. Silicon also forms chains, but NCERT notes they stop at about 7 or 8 atoms and are very reactive.
Where marks go
Question 25 of CBSE's 2026-27 Science sample paper asks why carbon forms millions of compounds but silicon, just below it, forms few. It is worth 2 marks. The 2026-27 Science marking scheme answers for both elements.
Carbon is small, so its C–C bonds are strong and stable, and it shows wide catenation. Silicon is larger, so its Si–Si bonds are weaker. So an answer about carbon alone covers half the comparison. See how to write answers for full marks.
Sources
Facts last checked against these sources on 30 September 2026.
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