Which point defect is observed in a crystal when a vacancy is created by an atom or ion missing from its normal position ?

Explanation

To solve the question regarding the point defect observed in a crystal when an atom or ion is missing from its normal position, we can follow these steps:

### Step-by-step Solution:

1. **Understanding Point Defects**:
- Point defects in a crystal lattice refer to disruptions at specific points in the structure. They can include vacancies, interstitials, and substitutions.

2. **Identifying the Type of Defect**:
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