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Carbon forms millions… (Class 10 Science SQP 2026-27, Q25)

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ScienceCBSE Class 10 · Sample paper, session 2026-27 · 2 marks · Very short answer

CBSE Class 10 Science sample paper 2026-27: question 25

From the official CBSE sample question paper for 2026-27, section B, question 25, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q25 · 2 marks · Very short answerCarbon and its Compounds

Carbon forms millions of compounds whereas silicon, which is just below it in the Periodic Table, forms a few compounds. Explain the reason for the difference in their ability to form compounds.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.

Hints

Open one hint at a time and try again before the next.

Hint 1

Think about the special property that lets carbon atoms join to one another in long chains.

Hint 2

Compare the atomic sizes of C and Si, and how size affects the strength of bonds between identical atoms.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Carbon atoms are very small, so the nucleus holds the shared electron pair strongly. Carbon therefore forms very strong and stable C–C bonds and can link with other carbon atoms to form long chains, branched chains and rings. This property is called catenation. Together with its tetravalency, this lets carbon form millions of compounds.

    1 mark

  2. Silicon is larger in size, so its nucleus holds the shared electrons less strongly. Si–Si bonds are weaker and less stable, and silicon shows catenation only to a limited extent (chains of about 7–8 atoms, which are reactive). Hence silicon forms only a few compounds.

    1 mark

Answer: Carbon's small size gives strong, stable C–C bonds and extensive catenation. Larger silicon forms weak Si–Si bonds and shows little catenation, so it forms few compounds.

Where the marks are

  • Small size of carbon gives strong, stable C–C bonds, so it shows extensive catenation (1 mark)
  • Larger size of silicon gives weaker Si–Si bonds and limited catenation, so it forms fewer compounds (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Carbon and its Compounds, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2026-27: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.