Q1. [3] medium thorough-understanding
Carbon and silicon both belong to the same group of the periodic table, yet the number of known carbon compounds far exceeds the number of known silicon compounds. Give two reasons why carbon's catenation leads to a vastly greater variety of stable compounds compared to silicon.
Generated by claude-sonnet-4-6 · 2026-06-26 01:09 · grounding rag
Model Answer
Two reasons why carbon's catenation produces far more stable compounds than silicon:
- Strength of C–C bond: The carbon–carbon bond is very strong and stable due to carbon's small atomic size, which allows the nucleus to hold shared electron pairs firmly. Silicon has larger atoms, so Si–Si bonds are much weaker, making silicon hydride chains (up to 7–8 atoms) highly reactive and unstable.
- Variety of bonding in chains: Carbon can form single, double, or triple bonds between atoms, and can arrange into straight chains, branched chains, or rings. Silicon lacks this ability, severely limiting the variety of compounds it can form.
Source: Chapter 4, Section 4.2 – Versatile Nature of Carbon
---
Explanation
- The examiner expects two distinct, well-explained points — each worth ~1.5 marks.
- Key terms to use: catenation, C–C bond strength, small atomic size, single/double/triple bonds, chains/rings.
- Don't just say "silicon is reactive" — explain why (larger atom → weaker bonds). That's the scoring detail.
- Avoid padding; two tight points with a reason each is all that's needed for 3 marks.