Assertion : Number of orbitals in 3rd shell is 9.
Reason : Number of orbitals for a particular value of `n = n^2` .

Options

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

Answer

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

### Step 1: Understand the Assertion
The assertion states that the number of orbitals in the third shell is 9.

### Step 2: Determine the Number of Orbitals in the Third Shell
The number of orbitals in a shell can be determined by the formula:
- For a given principal quantum number \( n \), the number of orbitals is given by \( n^2 \).

For the third shell:
- \( n = 3 \)
- Therefore, the number of orbitals = \( 3^2 = 9 \).

### Step 3: Verify the Reason
The reason states that the number of orbitals for a particular value of \( n \) is \( n^2 \).

### Step 4: Validate the Reason with Examples
- For \( n = 1 \):
- Number of orbitals = \( 1^2 = 1 \) (1s orbital)
- For \( n = 2 \):
- Number of orbitals = \( 2^2 = 4 \) (1s and 3p orbitals)
- For \( n = 3 \):
- Number of orbitals = \( 3^2 = 9 \) (1s, 3p, and 5d orbitals)

### Step 5: Conclusion
Both the assertion and the reason are correct:
- The assertion that the number of orbitals in the third shell is 9 is true.
- The reason that the number of orbitals for a particular value of \( n \) is \( n^2 \) is also true.

### Final Answer
Both the assertion and the reason are correct.

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