Which of the following statement regarding hydrides is not correct ?

Options

A. Ionic hydrides are crystalline , non - volatile and non - conducting in solid state
B. Electron - deficient hydrides act as Lewis acids or electron acceptors
C. Elements of group - 13 form electron - deficient hydrides
D. Elements of group 15-17 form electron - precise hydrides

Answer

To solve the question regarding which statement about hydrides is not correct, we will analyze each statement provided in the question step by step.

### Step 1: Analyze the First Statement
**Statement:** Ionic hydrides are crystalline, non-volatile, and non-conducting in solid state.

**Analysis:**
- Ionic hydrides, such as NaH and CaH2, are indeed crystalline solids.
- They are non-volatile because they do not easily vaporize at room temperature.
- In the solid state, they do not conduct electricity as they do not have free-moving ions.

**Conclusion:** This statement is **true**.

### Step 2: Analyze the Second Statement
**Statement:** Electron deficient hydrides act as a Lewis acid or electron acceptors.

**Analysis:**
- Electron deficient hydrides, such as those formed by Group 13 elements (e.g., BH3), indeed act as Lewis acids because they can accept electrons due to their incomplete octet.

**Conclusion:** This statement is **true**.

### Step 3: Analyze the Third Statement
**Statement:** Elements of Group 13 form electron deficient hydrides.

**Analysis:**
- Group 13 elements, such as boron and aluminum, form hydrides that are electron deficient (e.g., BH3, AlH3).

**Conclusion:** This statement is **true**.

### Step 4: Analyze the Fourth Statement
**Statement:** Elements of Group 15 and 17 form electron precise hydrides.

**Analysis:**
- Group 15 elements (like nitrogen and phosphorus) and Group 17 elements (like chlorine) form hydrides that are electron rich, not electron precise. For example, NH3 (ammonia) and PH3 (phosphine) are electron-rich hydrides.
- Therefore, the statement is incorrect because it mischaracterizes the nature of the hydrides formed by these groups.

**Conclusion:** This statement is **not correct**.

### Final Conclusion
The statement that is not correct is the fourth statement. Therefore, the answer to the question is that the fourth statement is the one that is incorrect.