Question

The upper level of valence band and lower level of conduction band overlap in the case of

• A. silicon
• B. copper
• C. carbon
• D. germanium

Answer 1

The Correct Option is B

In a conductor, such as copper, the upper level of the valence band and the lower level of the conduction band overlap, allowing electrons to move freely between these bands. This overlap enables electrical conductivity at room temperature, as electrons can easily jump from the valence band to the conduction band without any energy gap.

In contrast, semiconductors like silicon, carbon, and germanium have a distinct energy gap between the valence band and conduction band.

Thus, the correct answer is (B): copper.

Answer 2

In solid-state physics, the band structure of a material determines whether it is a conductor, semiconductor, or insulator. The material's electrical properties depend on the interaction between the valence band and the conduction band.

Conductors (like copper): In conductors, the valence band and the conduction band overlap, meaning that electrons can move freely between these bands even at low temperatures, enabling the flow of electric current. This overlap allows metals like copper to conduct electricity efficiently.

Semiconductors (like silicon, germanium): In semiconductors, the valence band and conduction band are separated by an energy gap (band gap), but electrons can be excited to the conduction band at higher temperatures or by external energy sources.

Insulators: The energy gap between the valence band and conduction band in insulators is large, preventing electrons from moving to the conduction band under normal conditions.

Therefore, the correct answer is (B) copper, as it is a metal where the upper level of the valence band and the lower level of the conduction band overlap.