Ca is the good reducing agent, because

Options

A. It has small size
B. It is the first member of group 2
C. It has one electron in outermost shell
D. It has the negative reduction potential

Answer

To determine why calcium (Ca) is a good reducing agent, we need to analyze the options provided and understand the properties of calcium in relation to its ability to act as a reducing agent.

### Step-by-Step Solution:

1. **Understanding Reducing Agents**:
- A reducing agent is a substance that donates electrons to another substance, thereby reducing it. In the process, the reducing agent itself gets oxidized.

2. **Analyzing the Options**:
- We have four options to evaluate whether they support the claim that calcium is a good reducing agent.

3. **Option 1: It has a small size**:
- As we move down a group in the periodic table, the size of the atoms increases due to the addition of electron shells. Calcium is larger than beryllium, the first member of group 2. Therefore, this option is incorrect.

4. **Option 2: It is the first member of group two**:
- The first member of group 2 is beryllium (Be), not calcium. Therefore, this option is also incorrect.

5. **Option 3: It has one electron in the outermost shell**:
- Calcium is in group 2 and has the electronic configuration of [Ar] 4s², meaning it has two electrons in its outermost shell, not one. Thus, this option is incorrect.

6. **Option 4: It has a negative reduction potential**:
- Calcium has a negative standard reduction potential, which indicates that it readily loses electrons (is oxidized) and can reduce other substances. This makes it a good reducing agent. Therefore, this option is correct.

7. **Conclusion**:
- The correct reason why calcium is a good reducing agent is that it has a negative reduction potential, which facilitates its ability to donate electrons and reduce other substances.

### Final Answer:
Calcium is a good reducing agent because it has a negative reduction potential.

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