Which of the following element have maximum tendency to form complex compound-

Options

A. `Be`
B. `Ba`
C. `Ca`
D. `Mg`

Explanation

To solve the question of which element has the maximum tendency to form complex compounds, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Complex Compounds**:
- Complex compounds are formed when a central metal atom or ion bonds with surrounding molecules or ions (ligands). The ability of an element to form such compounds depends on its ability to polarize the ligands.

2. **Identify the Elements**:
- The elements in question are from the S-block of the periodic table, specifically Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), and Barium (Ba).

3. **Degree of Polarization**:
- The tendency to form complex compounds is directly proportional to the degree of polarization. Polarization refers to the distortion of the electron cloud of a ligand by the electric field of a cation.

4. **Trends in the S-block Elements**:
- As we move down the group in the S-block elements, the size of the cation increases, which leads to a decrease in the charge density. This results in a decrease in the degree of polarization.
- Beryllium, being the smallest cation in the group, has the highest charge density and therefore the highest degree of polarization.

5. **Conclusion**:
- Since Beryllium has the maximum tendency to polarize ligands due to its small size and high charge density, it will have the maximum tendency to form complex compounds among the given options.

6. **Final Answer**:
- Therefore, the element with the maximum tendency to form complex compounds is **Beryllium (Be)**.