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Difficulty: HardConductors, Insulators, and Semiconductors

In electronics and solid-state physics, materials are fundamentally classified by the number of valence electrons in their outermost atomic shell and their conductivity characteristics. An element contains exactly four valence electrons in its outer shell, forming covalent bonds in a crystalline lattice that exhibits moderate resistivity at room temperature and increased conductivity as temperature rises. Which of the following substances possesses these specific atomic and electrical properties?

  1. A
    Copper
  2. SiliconAnswer
  3. C
    Mica
  4. D
    Aluminum

Answer

Silicon, because it is a semiconductor with four valence electrons in its outer shell and a negative temperature coefficient of resistance.
Silicon is an elemental semiconductor belonging to Group IV of the periodic table, meaning each atom has four valence electrons. In a solid crystal lattice, these four electrons form covalent bonds with adjacent atoms. At room temperature, thermal excitation frees a small fraction of these electrons across the narrow energy gap into the conduction band, giving silicon an intermediate level of conductivity that increases as thermal energy rises.

Step-by-Step Solution

1
Identify the material category based on the outer shell valence electron count.
An atom with exactly four valence electrons is classified as a semiconductor (Group IV element).
Good conductors typically have 1 to 3 valence electrons, semiconductors have exactly 4, and insulators generally have 5 to 8 tightly held valence electrons.
2
Evaluate the electrical conduction behavior described in the scenario.
The material exhibits moderate resistivity and a negative temperature coefficient of resistance (conductivity increases with temperature).
In intrinsic semiconductors, added thermal energy breaks covalent bonds, releasing electron-hole pairs into the conduction band to facilitate charge flow.
3
Match the specified atomic and electrical characteristics to the given material choices.
Silicon is a Group IV semiconductor, whereas copper and aluminum are conductors and mica is an insulator.
Silicon has an atomic number of 14 with an electron configuration of 2-8-4, giving it precisely four valence electrons.

Key Concept

Semiconductor atomic structure and valence electron properties
Estimated Time:1m 15s
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Topics

Conductors, Insulators, and Semiconductors

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