Assertion : `PF_(5),SF_(6)and H_(2)SO_(4)` are the examples of expanded octet molecules .
Reason : Octet rule is not applicable to the second period elements of the periodic table.

Options

A. both assertion and reason are true and reason is the correct explanation of assertion.
B. both assertion and reason are true but reason in not the correct explanation of assertion.
C. assertion is true but reason is false.
D. both assertion and reason are false.

Explanation

To solve the assertion and reason question regarding expanded octet molecules, we will analyze both the assertion and the reason step by step.

### Step 1: Understanding the Assertion
The assertion states that PF₅, SF₆, and H₂SO₄ are examples of expanded octet molecules.

- **PF₅ (Phosphorus Pentafluoride)**: Phosphorus has 5 valence electrons. In PF₅, phosphorus forms five bonds with fluorine atoms. This results in a total of 10 electrons around phosphorus, which exceeds the octet rule (8 electrons). Therefore, PF₅ is indeed an expanded octet molecule.

- **SF₆ (Sulfur Hexafluoride)**: Sulfur has 6 valence electrons. In SF₆, sulfur forms six bonds with fluorine atoms, leading to a total of 12 electrons around sulfur. This also exceeds the octet rule, confirming that SF₆ is an expanded octet molecule.

- **H₂SO₄ (Sulfuric Acid)**: In H₂SO₄, sulfur is bonded to four oxygen atoms (two with double bonds and two with single bonds). The total number of electrons around sulfur in this molecule is 12, which again exceeds the octet rule. Thus, H₂SO₄ is also an expanded octet molecule.

**Conclusion for Step 1**: The assertion is correct.

### Step 2: Understanding the Reason
The reason provided states that the octet rule is not applicable to the second period elements of the periodic table.

- The octet rule primarily applies to main group elements, particularly those in the second period (like carbon, nitrogen, oxygen, and fluorine). These elements typically follow the octet rule, meaning they tend to form bonds in such a way that they have 8 electrons in their valence shell.

- The assertion that the octet rule is not applicable to second period elements is incorrect. The octet rule is indeed applicable to these elements; it is the elements from the third period onwards (like phosphorus and sulfur) that can expand their octet due to the availability of d-orbitals.

**Conclusion for Step 2**: The reason is incorrect.

### Final Conclusion
- The assertion is true (PF₅, SF₆, and H₂SO₄ are expanded octet molecules).
- The reason is false (the octet rule is applicable to second period elements).

Thus, the correct answer is that the assertion is true, but the reason is false.

### Answer: Assertion is true, Reason is false.

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