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 given orders is incorrect, we will analyze the properties of the compounds and ions mentioned in the question. The properties we will consider include electronegativity, hydration energy, electrical conductance, and magnetic moment.

### Step-by-Step Solution:

1. **Electronegativity Order**:
- We analyze the electronegativity of CF4, CH4, and SiH4.
- CF4 (Carbon Tetrafluoride) has a highly electronegative fluorine atom, making carbon electropositive. Thus, CF4 is more electronegative than CH4 (where carbon and hydrogen have similar electronegativities) and SiH4 (where silicon is less electronegative than carbon).
- The order based on electronegativity is: CF4 > CH4 > SiH4. This order is correct.

2. **Hydration Energy Order**:
- Hydration energy is proportional to the charge-to-radius ratio of the ions.
- For Al³⁺, it has the highest charge and the smallest radius, thus the highest hydration energy.
- Be²⁺ has a smaller radius than Mg²⁺, leading to higher hydration energy for Be²⁺.
- Na⁺ has the least charge and thus the least hydration energy.
- The order based on hydration energy is: Al³⁺ > Be²⁺ > Mg²⁺ > Na⁺. This order is also correct.

3. **Electrical Conductance Order**:
- Smaller ions tend to have higher hydration, leading to lower electrical conductance due to crowding.
- Among F⁻, Cl⁻, and S²⁻, F⁻ is the smallest ion, leading to maximum crowding and thus the lowest electrical conductance.
- The expected order should be: S²⁻ > Cl⁻ > F⁻ (from highest to lowest conductance). If the given order states otherwise, it would be incorrect.

4. **Magnetic Moment Order**:
- For Ni⁴⁺, the electronic configuration is 3d⁶, which has 4 unpaired electrons.
- The magnetic moment is calculated using the formula: μ = √(n(n + 2)), where n is the number of unpaired electrons.
- For Ni⁴⁺, n = 4, thus μ = √(4(4 + 2)) = √24. This is the maximum among the given options.
- Therefore, the order based on magnetic moment is correct.

### Conclusion:
The order that is incorrect is the one related to electrical conductance. The correct order should reflect that F⁻ has the lowest conductance due to its smaller size and higher hydration, leading to maximum crowding.

### Final Answer:
The incorrect order is related to electrical conductance.

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