Which of the following statements is/are true for BaO and MgO ?

Options

A. BaO is more ionic than MgO
B. MgO is more ionic than BaO
C. BaO has a higher melting point than MgO
D. MgO has a higher melting point than BaO

Answer

To determine which statements are true for Barium Oxide (BaO) and Magnesium Oxide (MgO), we will analyze the properties of both compounds based on their ionic character and melting points.

### Step-by-Step Solution:

1. **Understanding Ionic Character**:
- Ionic character is influenced by the size of the cation. According to Fajans' rules, the larger the cation, the more ionic character the compound tends to have.
- Barium (Ba) is larger than Magnesium (Mg). Therefore, BaO will have a higher ionic character than MgO.

**Conclusion**: **Barium oxide (BaO) is more ionic than magnesium oxide (MgO)**. This statement is true.

2. **Analyzing Melting Points**:
- The melting point of ionic compounds is largely determined by their lattice energy. Lattice energy is the energy required to separate one mole of an ionic solid into its gaseous ions.
- The lattice energy is directly proportional to the charges of the ions and inversely proportional to the distance between the ions (R).
- For both BaO and MgO, the charges on the cations and anions are the same (both are +2 for the cation and -2 for the anion).
- However, the ionic radius of Ba is larger than that of Mg. This means that the distance (R) in BaO is greater than in MgO.
- Since lattice energy decreases with increasing distance, MgO will have a higher lattice energy compared to BaO.

**Conclusion**: **Magnesium oxide (MgO) has a higher melting point than barium oxide (BaO)**. This statement is also true.

### Final Statements:
- **Statement 1**: Barium oxide is more ionic than magnesium oxide. **(True)**
- **Statement 2**: Magnesium oxide has a higher melting point than barium oxide. **(True)**