(A) There are two nodal regions in 3s-orbital
(R) : There is no nodal plane in 3s orbital
The correct answer is

Options

A. Both (A) and (R) are true and (R) is the correct explanation of (A)
B. Both (A) and (R) are true and (R) is not the correct explanation of (A)
C. (A) is true but (R) is false
D. (A) is false but (R) is true

Answer

To solve the question regarding the assertion and reasoning statements about the 3s orbital, we will analyze both statements step by step.

### Step 1: Analyze the Assertion
The assertion states: "There are two nodal regions in 3s orbital."

- **Understanding Nodal Regions**: Nodal regions refer to areas in an orbital where the probability of finding an electron is zero. The total number of nodes in an orbital can be calculated using the formula:

\[ \text{Total number of nodes} = n - 1 \]

- **For the 3s Orbital**: Here, \( n = 3 \) (since it is the 3s orbital).

\[ \text{Total number of nodes} = 3 - 1 = 2 \]

Thus, the assertion is **true**.

### Step 2: Analyze the Reasoning
The reasoning states: "There is no nodal plane in 3s orbital."

- **Understanding Nodal Planes**: Nodal planes are specific types of nodes that correspond to angular nodes, which are determined by the azimuthal quantum number \( l \). The number of nodal planes is equal to \( l \).

- **For the 3s Orbital**: The value of \( l \) for an s orbital is 0 (since s orbitals have \( l = 0 \)). Therefore, the number of nodal planes is:

\[ \text{Number of nodal planes} = l = 0 \]

Thus, the reasoning is also **true**.

### Step 3: Determine the Relationship Between Assertion and Reasoning
Now, we need to assess whether the reasoning correctly explains the assertion.

- The assertion states that there are two nodal regions, which is true.
- The reasoning states that there are no nodal planes, which is also true.

However, the reasoning does not directly explain why there are two nodal regions. It simply states a fact about nodal planes. Therefore, while both statements are true, the reasoning does not provide a correct explanation for the assertion.

### Conclusion
Based on the analysis:

- Both the assertion (A) and reasoning (R) are true.
- However, R is not the correct explanation of A.

Thus, the correct answer is: **Option 2: Both A and R are true, but R is not the correct explanation of A.**

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