The number of incomplete orbits in inner transition elements is

Options

A. 1
B. 2
C. 3
D. 4

Explanation

To solve the question regarding the number of incomplete orbits in inner transition elements, we can follow these steps:

### Step-by-Step Solution:

1. **Identify Inner Transition Elements**:
- Inner transition elements are known as the f-block elements in the periodic table. They include the lanthanides (4f) and actinides (5f).

2. **Understand Electron Configuration**:
- The general electronic configuration for inner transition elements can be written as:
\[ n^2 n-1 d^{0-1} n-2 f^{1-14} \]
- Here, \( n \) represents the principal quantum number.

3. **Determine the Orbitals**:
- For inner transition elements, the last electrons enter the 4f and 5f orbitals.
- The 4f orbital can hold a maximum of 14 electrons, and the 5f orbital can also hold a maximum of 14 electrons.

4. **Count Incomplete Orbitals**:
- An incomplete orbital is one that does not have the maximum number of electrons it can hold.
- In the case of the f-block elements, both the 4f and 5f orbitals can be incomplete depending on the specific element in the series.
- Therefore, we can say there are two incomplete orbitals (4f and 5f).

5. **Include d-Orbitals**:
- Although the question specifically asks about f-orbitals, we can also consider the d-orbitals (n-1 d) which can be present in some of these elements.
- However, since the question focuses on inner transition elements, we primarily focus on the f-orbitals.

6. **Conclusion**:
- Based on the analysis, we conclude that the number of incomplete orbitals in inner transition elements is 3 (considering both the 4f and 5f orbitals, and the d-orbital).

### Final Answer:
The number of incomplete orbits in inner transition elements is **3**.