Which of the following statement (s) for crystal having schottky defect is/are correct

Options

A. Schottky defect arises due to absence of cation & anion from position which they are expected to occupy
B. The density of crystal having shottky defect is smaller than that of perfect crystal
C. Schottky defect are more common in co-valent compound with higher co-ordination number
D. The crystal having shottky defect is electrically neutral as a whole

Explanation

To determine which statements regarding a crystal with a Schottky defect are correct, we need to analyze the properties and characteristics of Schottky defects. Here’s a step-by-step solution:

### Step 1: Understand Schottky Defect
A Schottky defect occurs in ionic crystals when equal numbers of cations and anions are missing from their lattice sites. This defect maintains the electrical neutrality of the crystal.

**Hint:** Remember that Schottky defects involve the absence of both cations and anions.

### Step 2: Analyze the Statements
1. **Statement 1:** "Schottky defect arises due to absence of cation and anions from positions which they are expected to occupy."
- This statement is **correct** because Schottky defects are characterized by the absence of both types of ions from their lattice positions.

2. **Statement 2:** "The density of crystal having Schottky defect is smaller than that of perfect crystal."
- This statement is **correct** because the removal of ions leads to a decrease in mass without a significant change in volume, resulting in lower density.

3. **Statement 3:** "Schottky defects are more common in covalent compounds with higher coordination number."
- This statement is **incorrect** because Schottky defects are primarily found in ionic compounds, not covalent compounds. Ionic compounds are more likely to exhibit this type of defect due to the presence of both cations and anions.

4. **Statement 4:** "The crystal having Schottky defect is electrically neutral as a whole because of equal number of cations and anions are missing from the crystal."
- This statement is **correct** because the equal loss of cations and anions maintains the overall charge neutrality of the crystal.

### Step 3: Conclusion
Based on the analysis:
- **Correct Statements:** 1, 2, and 4
- **Incorrect Statement:** 3

Thus, the correct options are statements 1, 2, and 4.

**Final Answer:** Statements 1, 2, and 4 are correct.

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