Which of the following statements is wrong ?

Options

A. `Ti^(4+) and Ag^(+)` are repelled by magnetic field.
B. `Mn^(2+)` shows maximum magnetic character among the first transition series.
C. `Fe^(2+)` is more stavle than `Mn^(2+)` towards oxidation to + state.
D. Cr in `Cr_2O_7^(2-)` ion involves `sp^3d^2` hydridisation.

Answer

To determine which statement is incorrect, let's analyze each statement step by step.

### Step 1: Analyze Statement 1
**Statement:** Ti⁺⁴ and Ag⁺ are repelled by a magnetic field.

- **Explanation:** Paramagnetic substances have unpaired electrons and are attracted to magnetic fields, while diamagnetic substances have all paired electrons and are repelled by magnetic fields.
- **Ti⁺⁴:** Electronic configuration is [Ar] 3d⁰ (no unpaired electrons).
- **Ag⁺:** Electronic configuration is [Kr] 4d¹⁰ (also no unpaired electrons).
- **Conclusion:** Both Ti⁺⁴ and Ag⁺ have no unpaired electrons, so they are indeed repelled by a magnetic field. **This statement is true.**

### Step 2: Analyze Statement 2
**Statement:** Mn²⁺ shows maximum magnetic moment among the first transition series.

- **Explanation:** The magnetic moment is related to the number of unpaired electrons.
- **Mn²⁺:** Electronic configuration is [Ar] 3d⁵ 4s⁰ (five unpaired electrons).
- **Conclusion:** Since Mn²⁺ has the maximum number of unpaired electrons (5), it indeed shows the maximum magnetic moment among the first transition series. **This statement is true.**

### Step 3: Analyze Statement 3
**Statement:** Fe²⁺ is more stable than Mn²⁺ towards oxidation to the +3 state.

- **Explanation:** Stability towards oxidation can be assessed through electronic configurations.
- **Fe²⁺:** Electronic configuration is [Ar] 3d⁶ 4s⁰. Upon losing one electron to become Fe³⁺, it becomes [Ar] 3d⁵, which is half-filled and stable.
- **Mn²⁺:** Electronic configuration is [Ar] 3d⁵, which is already half-filled. Thus, it is less likely to lose an electron to form Mn³⁺.
- **Conclusion:** Fe²⁺ is indeed more stable towards oxidation to Fe³⁺ than Mn²⁺ is towards Mn³⁺. **This statement is true.**

### Step 4: Analyze Statement 4
**Statement:** Cr in Cr₂O₇²⁻ is involved in sp³d² hybridization.

- **Explanation:** To determine the hybridization, we need to look at the bonding and geometry.
- **Cr₂O₇²⁻:** Each chromium atom forms four sigma bonds with oxygen atoms (three double bonds and one single bond).
- **Hybridization:** The presence of four sigma bonds indicates that the hybridization is sp³ (not sp³d², which would indicate five bonds).
- **Conclusion:** Therefore, the statement that Cr in Cr₂O₇²⁻ is involved in sp³d² hybridization is incorrect. **This statement is false.**

### Final Answer
The incorrect statement is **Statement 4**.

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