If P, Q, R and S are elements of 3rd period of p-block in modern periodic table, among these one element is metal and rest are non-metals and their order of electronegativity is given as:
`P lt Q lt R lt S`
Q. Chloride compound of which element is hypovalent?

Options

A. S
B. Q
C. R
D. P

Explanation

To determine which element among P, Q, R, and S has a hypovalent chloride compound, we will analyze the elements based on their positions in the third period of the p-block and their electronegativity values.

### Step-by-Step Solution:

1. **Identify the Elements in the 3rd Period of the p-block**:
- The elements in the third period of the p-block are Aluminum (Al), Silicon (Si), Phosphorus (P), and Sulfur (S).
- Among these, Aluminum is a metal, while Silicon, Phosphorus, and Sulfur are non-metals.

2. **Understand the Electronegativity Order**:
- The given order of electronegativity is P < Q < R < S.
- Based on the periodic trends, we can assign the elements as follows:
- P = Al (metal)
- Q = Si (non-metal)
- R = P (non-metal)
- S = S (non-metal)

3. **Determine the Chloride Compounds**:
- Aluminum forms AlCl3.
- Silicon forms SiCl4.
- Phosphorus can form PCl5.
- Sulfur can form SCl6.

4. **Analyze the Valency of Each Chloride**:
- **AlCl3**: Aluminum has 3 valence electrons and forms 3 bonds with chlorine. This means it has only 6 electrons around it (not a complete octet), making it hypovalent.
- **SiCl4**: Silicon has 4 valence electrons and forms 4 bonds, achieving a complete octet (8 electrons).
- **PCl5**: Phosphorus has 5 valence electrons and can form 5 bonds, also achieving a complete octet (8 electrons).
- **SCl6**: Sulfur can expand its octet and form 6 bonds, exceeding the octet rule (hypervalent).

5. **Conclusion**:
- The only element that forms a hypovalent chloride compound is Aluminum (Al), which forms AlCl3.

### Final Answer:
The chloride compound of Aluminum (Al) is hypovalent.

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