Which of the following given statesment is incorrect?

Options

A. F-centres generation is responsible factor for imparting colour to the crystal
B. Frenkel defect is usually shown by ionic compound having low coordination number
C. Stoichiometry of crystal remains uneffected due to schottky defect
D. Density of crystal always increses due to susbtitutional impurity defect

Answer

To determine which of the given statements is incorrect, we need to analyze each statement one by one based on our knowledge of crystal defects and their effects.

### Step-by-Step Solution:

1. **Analyze the First Statement:**
- **Statement:** "App-Centered generation is responsible factor for impacting color to the crystal."
- **Analysis:** This statement is correct. App-Centered generation does lead to the excitation and de-excitation of electrons, which can affect the color of the crystal.

2. **Analyze the Second Statement:**
- **Statement:** "Frankl defect is usually shown by ionic compound having low coordination number."
- **Analysis:** This statement is also correct. The Frankl defect occurs when a smaller cation leaves its original position and occupies an interstitial site, which can lead to a reduction in coordination number.

3. **Analyze the Third Statement:**
- **Statement:** "Strychometry of a crystal remain unaffected due to Scott's defect."
- **Analysis:** This statement is correct. In Scott's defect, equal numbers of cations and anions are missing, which means the stoichiometry of the crystal remains constant.

4. **Analyze the Fourth Statement:**
- **Statement:** "Density of a crystal always increases due to substitutional impurity defect."
- **Analysis:** This statement is incorrect. The density of a crystal can either increase or decrease due to substitutional impurities depending on the size and mass of the substituting atoms compared to the original atoms. If the substituting atom is lighter or smaller, the density may decrease.

### Conclusion:
The incorrect statement is: "Density of a crystal always increases due to substitutional impurity defect."

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