Which of the following order is incorrect?

Options

A. Electronegativity of central atom: `CF_(4) gt CH_(4) gt SiH_(4)`
B. Hydration energy: `Al^(3+) gt Be^(2+) gt Mg^(2+) gt Na^(+)`
C. Electrical conductance: `F_((aq))^(-) gt Cl_((aq))^(-) gt S_((aq))^(2-)`
D. Magnetic moment: `Ni^(4+) gt V^(3+) gt Sr^(2+)`

Answer

To determine which of the following orders is incorrect, we will analyze the given options step by step.

### Step 1: Analyze Electronegativity of Central Atoms
- **Given Molecules**: CF4, CH4, SiH4
- **Central Atoms**: Carbon (C) in CF4 and CH4; Silicon (Si) in SiH4.
- **Electronegativity Trends**:
- Fluorine (F) is highly electronegative and pulls electron density towards itself in CF4, increasing the effective electronegativity of carbon.
- In CH4, carbon has a normal electronegativity.
- Silicon is below carbon in the periodic table, so its electronegativity is lower than that of carbon.
- **Order of Electronegativity**: CF4 > CH4 > SiH4
- **Conclusion**: This order is correct.

### Step 2: Analyze Hydration Energy
- **Given Ions**: Al³⁺, Be²⁺, Mg²⁺, Na⁺
- **Hydration Energy Trends**:
- Smaller ions have higher hydration energy due to higher charge density and effective nuclear charge (Z effective).
- Be²⁺ has a smaller radius than Mg²⁺, so Be²⁺ will have higher hydration energy.
- Al³⁺ has a smaller radius than Na⁺, so Al³⁺ will have higher hydration energy than Na⁺.
- **Order of Hydration Energy**: Al³⁺ > Be²⁺ > Mg²⁺ > Na⁺
- **Conclusion**: This order is correct.

### Step 3: Analyze Electrical Conductance
- **Given Anions**: F⁻, Cl⁻, S²⁻
- **Conductance Trends**:
- Smaller ions are more hydrated and hinder the movement of ions in solution, leading to lower electrical conductivity.
- F⁻ is the smallest anion, followed by Cl⁻ and then S²⁻.
- **Order of Conductance**: S²⁻ > Cl⁻ > F⁻
- **Conclusion**: If the statement claims F⁻ has the highest conductance, it is incorrect.

### Step 4: Analyze Magnetic Moment
- **Given Ion**: Ni⁴⁺
- **Electron Configuration**: Ni (atomic number 28) in +4 oxidation state has the configuration of Argon 4s² 3d⁴.
- **Unpaired Electrons**: In Ni⁴⁺, there are 4 unpaired electrons.
- **Magnetic Moment Calculation**:
- Formula: μ = √(n(n + 2)), where n is the number of unpaired electrons.
- μ = √(4(4 + 2)) = √(24)
- **Conclusion**: The calculation is correct.

### Final Conclusion
- The incorrect order is found in the electrical conductance of the anions. The correct order is S²⁻ > Cl⁻ > F⁻, but the option stated that F⁻ has the highest electrical conductance, which is incorrect.

### Answer
**The incorrect order is in option C: F⁻ has the highest electrical conductance, which is wrong.**

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