Which one of the following statement is wrong ?

Options

A. The conducitivity of metals decreases with increases in temperature .
B. The conducitvity of semiconductor increases with increases in temperature.
C. There is no superconductor at room temperature
D. Ionic solids conduct electricity due to presence of ions .

Explanation

To solve the question "Which one of the following statement is wrong?", we need to analyze each of the provided statements regarding electrical conductivity in different materials.

### Step-by-Step Solution:

1. **Understanding the First Statement**:
- The first statement claims that the conductivity of metal decreases with increasing temperature.
- In metals, as temperature increases, the positive ions (kernels) vibrate more vigorously, which hinders the flow of electrons. This results in decreased conductivity.
- **Conclusion**: This statement is **correct**.

2. **Analyzing the Second Statement**:
- The second statement states that the conductivity of semiconductors increases with an increase in temperature.
- In semiconductors, as temperature rises, electrons gain enough energy to jump from the valence band to the conduction band, thereby increasing conductivity.
- **Conclusion**: This statement is **correct**.

3. **Evaluating the Third Statement**:
- The third statement mentions that there is no superconductor at room temperature, and superconductivity can only be achieved at very low temperatures.
- This is true as superconductivity occurs at temperatures close to absolute zero, typically around 4 to 5 Kelvin.
- **Conclusion**: This statement is **correct**.

4. **Examining the Fourth Statement**:
- The fourth statement asserts that ionic solids conduct electricity due to the presence of ions.
- Ionic solids do contain ions, but they do not conduct electricity in the solid state because the ions are fixed in place and cannot move freely. They only conduct electricity when melted or dissolved in water, where the ions can move freely.
- **Conclusion**: This statement is **wrong** because conductivity in ionic solids depends on the mobility of ions, not just their presence.

### Final Answer:
The wrong statement is the **fourth statement**.

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