Which of the following metal is highest electropositive (metallic) in nature?

Options

A. Be
B. Rb
C. Mn
D. Tl

Explanation

To determine which of the given metals is the most electropositive, we need to analyze the ionization energy of each metal. Electropositivity is inversely related to ionization energy; the lower the ionization energy, the more electropositive the element is.

### Step-by-Step Solution:

1. **Understanding Electropositivity**:
- Electropositivity refers to the ability of an element to donate electrons and form positive ions. Metals tend to be electropositive, and this property increases as we move down a group in the periodic table.

2. **Identify the Elements**:
- The question provides four options. Let's assume the options are Beryllium (Be), Rubidium (Rb), Thallium (Tl), and Boron (B).

3. **Analyze Ionization Energy**:
- **Beryllium (Be)**:
- Electronic configuration: 1s² 2s².
- It has a high ionization energy due to its stable electron configuration (full outer shell). Thus, it is not very electropositive.
- **Rubidium (Rb)**:
- Rubidium is an alkali metal with the electronic configuration [Kr] 5s¹.
- Alkali metals have low ionization energies, and as we move down the group, the ionization energy decreases. Therefore, Rb has a very low ionization energy and is highly electropositive.
- **Thallium (Tl)**:
- Electronic configuration: [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹.
- Thallium has a relatively higher ionization energy compared to Rb, making it less electropositive.
- **Boron (B)**:
- Electronic configuration: 1s² 2s² 2p¹.
- Boron has a higher ionization energy than both Rb and Tl, indicating it is not very electropositive.

4. **Conclusion**:
- Among the given metals, Rubidium (Rb) has the lowest ionization energy and is therefore the most electropositive metal.

### Final Answer:
Rubidium (Rb) is the most electropositive metal among the given options.

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