Band gaps of elements — match each element (List I) with an approximate energy band gap value at room temperature (List II). List I (Element) A. C (diamond form) B. Si C. Ge D. Sn E. Pb List II (Approx. band gap Eg) 1. 7 eV 2. 1.15 eV 3. 0.75 eV 4. 0.1 eV 5. 0 eV (metal)
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AA-2, B-3, C-4, D-5, E-1
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BA-1, B-2, C-3, D-4, E-5
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CA-3, B-1, C-2, D-5, E-4
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DA-4, B-5, C-1, D-2, E-3
Answer
Correct Answer: A-1, B-2, C-3, D-4, E-5
Explanation
Introduction / Context:Band gap values classify materials as insulators, semiconductors, or metals. Knowing typical Eg helps predict conductivity, optical properties, and device applications.
Given Data / Assumptions:
- Values are approximate room-temperature band gaps for the elemental forms listed.
- Diamond (C) is a wide-bandgap insulator; Si and Ge are classic semiconductors; Sn and Pb behave as semimetal/metal with very small or zero gaps.
Concept / Approach:
Map each element to a representative Eg: diamond has a very large gap; Si is about 1.1 eV; Ge is below 1 eV; gray tin can be near-semimetal with very small Eg; metals like Pb have Eg ≈ 0.
Step-by-Step Solution:
A (C) → wide band gap → ~7 eV → 1.B (Si) → ~1.12 eV → 2.C (Ge) → ~0.66–0.75 eV → 3.D (Sn) → ~0.1 eV (very small) → 4.E (Pb) → metal → 0 eV → 5.Verification / Alternative check:
Reference semiconductor tables place Si at ~1.12 eV and Ge at ~0.66 eV; diamond is often quoted 5.5–7 eV depending on definition; metals have overlapping bands yielding Eg ≈ 0.
Why Other Options Are Wrong:
- Swapping Si and Ge contradicts well-known semiconductor parameters.
- Assigning nonzero Eg to Pb contradicts metallic behavior.
- Placing diamond at a low Eg conflicts with its insulating nature.
Common Pitfalls:
Confusing indirect vs. direct gaps; the magnitude still orders as diamond > Si > Ge > Sn ≈ Pb.
Final Answer:
A-1, B-2, C-3, D-4, E-5