The decreasing order of the second ionization potential of Mg, Ca and Ba is

Options

A. `MggtCagtBa`
B. `CagtBagtMg`
C. `BagtMggtCa`
D. `MggtBagtCa`

Explanation

To determine the decreasing order of the second ionization potential of magnesium (Mg), calcium (Ca), and barium (Ba), we need to consider the following steps:

### Step 1: Understand Ionization Potential
Ionization potential (IP) is the energy required to remove an electron from an atom in the gaseous state. The second ionization potential refers to the energy required to remove a second electron after the first has already been removed.

### Step 2: Analyze the Group Trend
In the periodic table, magnesium, calcium, and barium belong to Group 2 (the alkaline earth metals). As we move down the group from magnesium to barium, the atomic size increases. This is due to the addition of electron shells, which increases the distance between the nucleus and the valence electrons.

### Step 3: Relationship between Size and Ionization Potential
The ionization potential generally decreases down a group. This is because the increased distance between the nucleus and the outermost electrons results in a weaker attraction, making it easier to remove electrons. Therefore, the second ionization potential will also follow this trend.

### Step 4: Compare the Elements
- **Magnesium (Mg)**: Has the smallest atomic size among the three, leading to the highest second ionization potential.
- **Calcium (Ca)**: Larger than magnesium but smaller than barium, resulting in a lower second ionization potential than magnesium but higher than barium.
- **Barium (Ba)**: Has the largest atomic size, leading to the lowest second ionization potential.

### Step 5: Conclusion
Based on the analysis, the decreasing order of the second ionization potential for Mg, Ca, and Ba is:
**Mg > Ca > Ba**

### Final Answer
The decreasing order of the second ionization potential of Mg, Ca, and Ba is:
**Mg > Ca > Ba**