Nature of a covalent bond in semiconductor crystals Evaluate the claim: “A covalent bond is formed when atoms lose valence electrons.” Decide whether this statement accurately describes covalent bonding as found in silicon or germanium lattices.

Difficulty: Easy

Correct Answer: Incorrect

Explanation:


Introduction / Context:
Covalent bonding explains how group-IV semiconductors form stable crystal lattices and why their electrical properties are sensitive to defects and temperature. Misstating the nature of covalent bonds can confuse learners about what keeps the lattice intact and how doping works.



Given Data / Assumptions:

  • Semiconductor crystals like silicon and germanium have tetrahedral bonding.
  • Basic chemistry definitions apply: covalent vs. ionic bonding.


Concept / Approach:
A covalent bond forms when atoms share pairs of valence electrons. In crystalline silicon, each atom shares one electron with each of four neighbors, forming four covalent bonds. In contrast, ionic bonding involves electron transfer (loss by one atom, gain by another), creating ions bound by electrostatic attraction. Therefore, “losing valence electrons” describes ionic, not covalent, bonding.



Step-by-Step Solution:

Identify bond type in Si/Ge: covalent (shared electron pairs).Contrast with ionic: electrons are transferred, forming cations/anions.Apply to the claim: it describes ionic behavior, not covalent.Conclusion: the statement is incorrect for covalent bonding.


Verification / Alternative check:
Intro chemistry texts and semiconductor physics books consistently define covalent bonds via shared electron pairs (e.g., H–H, C–C bonds), including the diamond lattice of Si/Ge.



Why Other Options Are Wrong:

Correct: contradicts the standard definition.Correct only for ionic crystals: even here, bonding is not covalent; it is ionic, so the phrasing still mismatches.Correct at very high doping levels: heavy doping perturbs the lattice electrically, not the fundamental bonding mechanism.


Common Pitfalls:
Assuming “losing electrons” is a universal mechanism. In covalent solids, atoms share electrons; they do not permanently lose them to neighbors.



Final Answer:
Incorrect

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