Assertion: Atomic size of As is less than that of P.
Reason: Atomic size increases along a period.

Options

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

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states that the atomic size of Arsenic (As) is less than that of Phosphorus (P).

- **Fact Check**: Phosphorus is located in the 3rd period of the periodic table, while Arsenic is located in the 4th period. Generally, atomic size increases as we move down a group in the periodic table due to the addition of electron shells.

### Step 2: Understand the Reason
The reason states that atomic size increases along a period.

- **Fact Check**: This statement is incorrect. Atomic size generally decreases across a period from left to right due to the increase in nuclear charge, which pulls the electrons closer to the nucleus.

### Step 3: Compare the Assertion and Reason
Since the assertion claims that As has a smaller atomic size than P, and the reason provided is incorrect, we need to conclude the truth values of both statements.

- **Assertion**: False (As is larger than P)
- **Reason**: False (Atomic size does not increase along a period; it decreases)

### Conclusion
Both the assertion and the reason are false. Therefore, the correct answer is that both statements are incorrect.

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