In which of the following elements one electron is present in 5d orbitals ?

Options

A. Gd and Yb
B. Gd and Tm
C. Gd and Lu
D. Ho and Lu

Explanation

To determine which of the following elements has one electron present in the 5d orbitals, we need to analyze the electron configurations of the given elements. The relevant elements are typically found in the d-block and f-block of the periodic table.

### Step-by-Step Solution:

1. **Identify the Elements**:
We need to look at the elements provided in the options. The question does not specify the options, but we will consider common elements that may include Gadolinium (Gd), Ytterbium (Yb), Thulium (Tm), Lutetium (Lu), and Holmium (Ho).

2. **Understand the Electron Configuration**:
- The d-block elements fill their d orbitals, while the f-block elements fill their f orbitals.
- The 5d orbitals start filling after the 4f orbitals are filled.

3. **Check the Electron Configuration of Each Element**:
- **Gadolinium (Gd)**: Atomic number 64
- Configuration: [Xe] 4f^7 5d^1 6s^2
- **Conclusion**: 1 electron is in the 5d orbital.

- **Ytterbium (Yb)**: Atomic number 70
- Configuration: [Xe] 4f^14 6s^2
- **Conclusion**: No electrons in the 5d orbital.

- **Thulium (Tm)**: Atomic number 69
- Configuration: [Xe] 4f^13 6s^2
- **Conclusion**: No electrons in the 5d orbital.

- **Lutetium (Lu)**: Atomic number 71
- Configuration: [Xe] 4f^14 5d^1 6s^2
- **Conclusion**: 1 electron is in the 5d orbital.

- **Holmium (Ho)**: Atomic number 67
- Configuration: [Xe] 4f^11 6s^2
- **Conclusion**: No electrons in the 5d orbital.

4. **Summarize Findings**:
- From the analysis, Gadolinium (Gd) and Lutetium (Lu) both have one electron in the 5d orbital.

5. **Select the Correct Option**:
If the options provided included pairs of elements, the correct answer would be the one that includes Gadolinium and Lutetium.

### Final Answer:
The elements that have one electron in the 5d orbitals are **Gadolinium (Gd)** and **Lutetium (Lu)**.