Which of the following is true ?

Options

A. The electron density in the xy- plane in `3d_(xy)` orbital is zero
B. The electron density in the xy- and xz plane in `3d_(yz)` orbital is zero
C. The electron density in the xy- plane in `3d_(x^(2)` orbital is zero
D. Pauli excussion principle is folloed by bosons which have integral spin

Explanation

To determine which of the statements is true, we will analyze each statement one by one.

### Step 1: Analyze the first statement
**Statement 1:** The electron density in the xy plane in the 3d xy orbital is zero.

- The 3d xy orbital has a specific shape that allows for electron density in the xy plane. The orbital is oriented in such a way that it has lobes in the xy plane. Therefore, the electron density in the xy plane is not zero.

**Conclusion:** This statement is **false**.

### Step 2: Analyze the second statement
**Statement 2:** The electron density in the xy and xz planes in the 3d yz orbital is equal to 0.

- The 3d yz orbital has lobes that extend along the y and z axes. Therefore, it also has electron density in the xy and xz planes. The presence of lobes indicates that electron density is not zero in these planes.

**Conclusion:** This statement is **false**.

### Step 3: Analyze the third statement
**Statement 3:** The electron density in the xy plane in the 3d x² orbital is equal to zero.

- The 3d x² orbital has its lobes oriented along the x-axis and y-axis, but it does not have lobes in the xy plane. Therefore, the electron density in the xy plane for the 3d x² orbital is indeed zero.

**Conclusion:** This statement is **true**.

### Step 4: Analyze the fourth statement
**Statement 4:** Pauli's exclusion principle is followed by bosons which have integral spin.

- Pauli's exclusion principle applies to fermions, which are particles with half-integer spin. Bosons, which have integral spin, do not follow this principle and can occupy the same quantum state. Therefore, this statement is incorrect.

**Conclusion:** This statement is **false**.

### Final Answer
Based on the analysis, the only true statement is **Statement 3**: The electron density in the xy plane in the 3d x² orbital is equal to zero.

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