In a good conductor, what is the energy gap between the
conduction band and the valence band.?

Explanation

To answer the question regarding the energy gap between the conduction band and the valence band in a good conductor, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Bands**: In solid-state physics, materials have two important energy bands: the conduction band (CB) and the valence band (VB). The conduction band is where electrons can move freely and contribute to electrical conduction, while the valence band is where electrons are bound to atoms.

2. **Characteristics of Good Conductors**: Good conductors, such as metals, have a unique property where the conduction band and the valence band overlap. This means that there is no energy gap between the two bands.

3. **Energy Gap Definition**: The energy gap (or band gap) is defined as the energy difference between the top of the valence band and the bottom of the conduction band. In good conductors, since these two bands overlap, the energy gap is effectively zero.

4. **Conclusion**: Therefore, in a good conductor, the energy gap between the conduction band and the valence band is **0 eV** (zero electron volts).

### Final Answer:
In a good conductor, the energy gap between the conduction band and the valence band is **0 eV**.

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