Atomic arrangement in elemental silicon: Silicon atoms bond together in what kind of orderly three-dimensional structure?

Introduction / Context:
The physical arrangement of atoms in silicon governs its electronic band structure and, consequently, device properties. Integrated circuits are fabricated on crystalline wafers with long-range order, enabling precise doping and anisotropic processes like etching and epitaxy.

Given Data / Assumptions:

• Elemental silicon at room temperature.
• Bulk material used for wafers (not amorphous thin films).
• Covalent bonding is the mechanism, but the question asks for the large-scale structure.

Concept / Approach:

Silicon forms a diamond-cubic crystal lattice. Each atom shares electrons with four neighbors (covalent bonds), producing a periodic three-dimensional arrangement. The term that captures this ordered structure is “crystal.” “Covalent bond” describes bonding, not the overall arrangement; “semiconductor” describes electronic behavior, not the geometry.

Step-by-Step Solution:

Verification / Alternative check:

X-ray diffraction patterns of silicon show sharp Bragg peaks consistent with a crystalline lattice, confirming the ordered structure.

Why Other Options Are Wrong:

• Covalent bond: microscopic bonding type, not the macroscopic structure.
• Semiconductor: material class by bandgap, not a structural term.
• Valence orbit: atomic electron shell concept, not a bulk structure.
• Amorphous matrix: lacks long-range order; not applicable to standard wafer silicon.

Common Pitfalls:

• Confusing chemical bonding terms with crystallographic structure terms.
• Assuming all silicon used in electronics is amorphous; most ICs use crystalline wafers.

Final Answer:

crystal