Which one of the following does not correctly represent the correct order of the property indicated against it ?

Options

A. `Ti ltVlt Crlt Mn`: increasing number of oxidation states
B. `Ti^(3+) lt V^(3+) lt Cr^(3+)lt Mn^(3+)` increasing magnetic moment
C. `Ti ltV ltCr ltMn` increasing melting points
D. `TiltV ltMnltCr`:increasing 2nd ionization enthalpy

Answer

To solve the question of which order does not correctly represent the indicated property, we will analyze each option provided in the question step by step.

### Step 1: Analyze the Order of Oxidation States
- **Elements**: Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn)
- **Oxidation States**:
- Ti: +4 (highest)
- V: +5 (highest)
- Cr: +6 (highest)
- Mn: +7 (highest)
- **Correct Order**: Ti < V < Cr < Mn
- **Conclusion**: This order is correct.

### Step 2: Analyze the Order of Magnetic Moments
- **Ions**: Ti³⁺, V³⁺, Cr³⁺, Mn³⁺
- **Electron Configurations**:
- Ti³⁺: 3d¹
- V³⁺: 3d²
- Cr³⁺: 3d³
- Mn³⁺: 3d⁴
- **Magnetic Moment**: Higher number of unpaired electrons leads to higher magnetic moments.
- **Correct Order**: Ti < V < Cr < Mn (based on increasing number of unpaired electrons)
- **Conclusion**: This order is correct.

### Step 3: Analyze the Order of Melting Points
- **Elements**: Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn)
- **Melting Points**:
- Ti: High
- V: Higher
- Cr: Highest
- Mn: Abnormally low due to stable configuration and weak intermetallic bonding.
- **Correct Order**: Ti < V < Cr < Mn (but Mn has a lower melting point than expected)
- **Conclusion**: This order is incorrect.

### Step 4: Analyze the Order of Second Ionization Enthalpy
- **Elements**: Ti, V, Cr, Mn
- **Trends**: Generally, the second ionization enthalpy increases across the period due to increased nuclear charge.
- **Correct Order**: Ti < V < Cr < Mn (Cr has a higher second ionization enthalpy due to its stable electronic configuration)
- **Conclusion**: This order is correct.

### Final Conclusion
The order that does not correctly represent the property indicated is the order of increasing melting points: **Ti < V < Cr < Mn** (as Mn has an abnormally low melting point).

### Answer
**Option C** does not correctly represent the order of melting points.

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