Which of the following represents the incorrect order of properties ?

Options

A. `NaCl lt MgCl_(2) lt AlCl_(3) lt SiCl_(4)` ( order of ionic character )
B. `BeCO_(3) lt MgCO_(3) lt CaCO_(3) lt BaCO_(3)`
( order of thermal stability)
C. `LiH gt NaH gt KH gt RbH gt CsH `
( order of thermal stability )
D. `BeSO_(4) gt MgSO_(4) gt CaSO_(4) gt BaSO_(4) `
( Order of solubility in water )

Answer

To determine which of the given arrangements represents the incorrect order of properties, we will analyze each option step by step.

### Step 1: Analyze Ionic Character
1. **Given Compounds**: NaCl, MgCl2, AlCl3, SiCl4
2. **Concept**: Ionic character is influenced by the charge and size of the cation. Higher charge and smaller size lead to higher ionic character.
3. **Cations**:
- Na⁺ (charge +1)
- Mg²⁺ (charge +2)
- Al³⁺ (charge +3)
- Si⁴⁺ (charge +4)
4. **Trend**: As we move from Na⁺ to Si⁴⁺, the charge increases and size decreases, leading to a decrease in ionic character.
5. **Correct Order**: NaCl > MgCl2 > AlCl3 > SiCl4 (correct trend).
6. **Conclusion**: The arrangement for ionic character is correct.

### Step 2: Analyze Thermal Stability of Carbonates
1. **Given Compounds**: BeCO3, MgCO3, CaCO3, BaCO3
2. **Concept**: Thermal stability of polyatomic ions is inversely proportional to charge density (charge/size).
3. **Cations**:
- Be²⁺ (small size, high charge density)
- Mg²⁺ (medium size, medium charge density)
- Ca²⁺ (larger size, lower charge density)
- Ba²⁺ (largest size, lowest charge density)
4. **Trend**: As we go down the group, the charge density decreases, leading to increased thermal stability.
5. **Correct Order**: BaCO3 > CaCO3 > MgCO3 > BeCO3 (correct trend).
6. **Conclusion**: The arrangement for thermal stability is correct.

### Step 3: Analyze Thermal Stability of Hydrides
1. **Given Compounds**: LiH, NaH, KH, RbH, CsH
2. **Concept**: For monoatomic ions, thermal stability is proportional to lattice energy (charge/size).
3. **Cations**:
- Li⁺ (smallest size)
- Na⁺ (larger than Li⁺)
- K⁺ (larger than Na⁺)
- Rb⁺ (larger than K⁺)
- Cs⁺ (largest size)
4. **Trend**: As we go down the group, size increases, leading to decreased thermal stability.
5. **Correct Order**: CsH < RbH < KH < NaH < LiH (correct trend).
6. **Conclusion**: The arrangement for thermal stability is correct.

### Step 4: Analyze Solubility in Water
1. **Given Compounds**: BeSO4, MgSO4, CaSO4, BaSO4
2. **Concept**: Solubility is influenced by charge and size; smaller cations with higher charge lead to higher solubility.
3. **Cations**:
- Be²⁺ (smallest size, highest hydrolysis)
- Mg²⁺ (larger than Be²⁺)
- Ca²⁺ (larger than Mg²⁺)
- Ba²⁺ (largest size, lowest hydrolysis)
4. **Trend**: As we go down the group, size increases and hydrolysis decreases, leading to decreased solubility.
5. **Correct Order**: BeSO4 > MgSO4 > CaSO4 > BaSO4 (correct trend).
6. **Conclusion**: The arrangement for solubility is correct.

### Final Conclusion
After analyzing all four properties, we find that the first arrangement regarding ionic character (NaCl, MgCl2, AlCl3, SiCl4) is the incorrect order of properties.