A : the number of angular nodes in ` 3d _(z^2) ` is zero
R : Number of angular nodes of atomic orbitals is equal to value of l.

Options

A. IF both assertion & reason are true and the reason is the correct explanation of the assertion then mark
B. IF both assertion & reason are true but the reason is not the correct explanation of the assertion , then mark
C. IF assertion is true statement but reason is false , then mark
D. If both assertion and reason are false statements then mark

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided.

**Assertion (A):** The number of angular nodes in `3d_(z^2)` is zero.

**Reason (R):** The number of angular nodes of atomic orbitals is equal to the value of l.

### Step-by-Step Solution:

1. **Understanding Angular Nodes:**
- Angular nodes are regions where the probability of finding an electron is zero. The number of angular nodes in an atomic orbital is determined by the azimuthal quantum number (l).

2. **Identifying the Quantum Numbers:**
- For the `3d` orbital, the principal quantum number (n) is 3 and the azimuthal quantum number (l) for d-orbitals is 2.

3. **Applying the Formula:**
- The formula for the number of angular nodes is given by:
\[ \text{Number of angular nodes} = l \]
- According to this formula, for a `3d` orbital, the expected number of angular nodes would be 2 (since l = 2).

4. **Analyzing the `3d_(z^2)` Orbital:**
- The `3d_(z^2)` orbital has a specific shape: it consists of two lobes along the z-axis and a ring in the xy-plane.
- The presence of the ring in the xy-plane indicates that there is a nodal plane in that region.

5. **Determining the Actual Number of Angular Nodes:**
- In the case of the `3d_(z^2)` orbital, the angular node is effectively zero because the lobes do not create any additional nodal planes. The probability of finding an electron is not zero in the z-direction, and thus the assertion that the number of angular nodes is zero is correct.

6. **Evaluating the Reason:**
- The reason states that the number of angular nodes is equal to the value of l, which is true in general. However, it does not correctly explain why the `3d_(z^2)` orbital has zero angular nodes. Instead, it should consider the specific shape of the orbital.

7. **Conclusion:**
- The assertion is true, but the reason does not correctly explain the assertion. Therefore, the correct option is that both assertion and reason are true, but the reason is not the correct explanation of the assertion.

### Final Answer:
- The correct option is: Both assertion and reason are true, but the reason is not the correct explanation of the assertion.