Intrinsic semiconductor valence: Intrinsic (pure) group-IV semiconductor materials such as silicon and germanium are characterized by a valence shell containing how many electrons?

Introduction / Context:
Covalent bonding in crystals like silicon and germanium arises from the valence electrons of group-IV atoms. The number of valence electrons determines how atoms bond in the lattice and underlies why group-III and group-V dopants create holes and electrons, respectively.

Given Data / Assumptions:

• Intrinsic semiconductor is undoped (pure).
• Focus is on elemental semiconductors silicon (Si) and germanium (Ge).
• Periodic table group determines valence electron count.

Concept / Approach:
Group-IV elements have four valence electrons. In the diamond cubic lattice, each atom forms four covalent bonds with neighbors, sharing electrons to complete octets. This explains the sensitivity of conductivity to dopants: adding trivalent (3) or pentavalent (5) atoms introduces holes or extra electrons, shifting carrier balances strongly.

Step-by-Step Solution:

Verification / Alternative check:
Electronic configurations: Si [Ne] 3s^2 3p^2 and Ge [Ar] 3d^10 4s^2 4p^2 both show four valence electrons (s^2 p^2), agreeing with group-IV placement.

Why Other Options Are Wrong:

• 1 or 2: Typical of alkali/alkaline earth metals (groups I and II), not semiconductors.
• 6: Group-VI chalcogens, not group-IV semiconductors.

Common Pitfalls:
Confusing valence count with the total number of electrons; only the outer-shell electrons participate in bonding and conduction.

Final Answer:
4