Which of the following arrangements represent the correct order of the property stated against it ?
(i) `Ni^(2+) lt Co^(2+) lt Fe^(2+) lt Mn^(2+)` : ionic size
(ii) `Co^(3+) lt Fe^(3+) lt Cr^(3+) lt Sc^(3+)` : stability in aqueious solution
(iii) `Sc lt Ti lt Cr lt Mn` : number of oxidation states
(iv) `V^(2+) lt Cr^(2+) lt Mn^(2+) lt Fe^(2+)` : paramagnetic behaviour

Options

A. 1. Sc < Ti < Cr < Mn : number of oxidation states
B. 2. `V^(2+) ltCr^(2+) ltMn^(2+) ltFe^(2+)` : paramagnetic behaviour
C. 3. `Ni^(2+) lt Co^(2+) ltFe^(2+) ltMn^(2+)` : ionic size
D. 4. `Co^(3+) lt Fe^(3+) lt Cr^(3+) lt Sc^(3+)` : stability in aqueous solution.

Explanation

To solve the question regarding the correct order of properties for the given ions and elements, we will analyze each statement one by one.

### Step 1: Analyze Ionic Size
**Statement (i):** `Ni^(2+) < Co^(2+) < Fe^(2+) < Mn^(2+)`

- **Explanation:** Ionic size generally decreases across a period due to increasing nuclear charge, which pulls the electrons closer to the nucleus. In the case of transition metals, the ionic size also depends on the number of d-electrons and their arrangement.
- **Correct Order:** The correct order of ionic sizes for these ions is actually `Mn^(2+) > Fe^(2+) > Co^(2+) > Ni^(2+)`. Thus, this statement is **incorrect**.

### Step 2: Analyze Stability in Aqueous Solution
**Statement (ii):** `Co^(3+) < Fe^(3+) < Cr^(3+) < Sc^(3+)`

- **Explanation:** The stability of metal ions in aqueous solution generally decreases as we move from left to right in the d-block due to increasing positive charge and the corresponding increase in effective nuclear charge. Scandium (Sc) has a +3 oxidation state and is less stable compared to the others.
- **Correct Order:** The correct order for stability in aqueous solution is `Sc^(3+) < Cr^(3+) < Fe^(3+) < Co^(3+)`. Thus, this statement is **incorrect**.

### Step 3: Analyze Number of Oxidation States
**Statement (iii):** `Sc < Ti < Cr < Mn`

- **Explanation:** The number of oxidation states increases as we move from Scandium to Manganese. Scandium has +2 and +3 oxidation states, Titanium has +2, +3, and +4, Chromium has +2, +3, +6, and Manganese has +2, +3, +4, +6, and +7.
- **Correct Order:** The correct order based on the number of oxidation states is `Sc < Ti < Cr < Mn`. Thus, this statement is **correct**.

### Step 4: Analyze Paramagnetic Behavior
**Statement (iv):** `V^(2+) < Cr^(2+) < Mn^(2+) < Fe^(2+)`

- **Explanation:** Paramagnetism is due to the presence of unpaired electrons. The electronic configurations are as follows:
- V^(2+): [Ar] 3d³ (3 unpaired electrons)
- Cr^(2+): [Ar] 3d⁴ (4 unpaired electrons)
- Mn^(2+): [Ar] 3d⁵ (5 unpaired electrons)
- Fe^(2+): [Ar] 3d⁶ (4 unpaired electrons, but with 4 unpaired in the high spin state)

- **Correct Order:** The correct order of paramagnetic behavior based on unpaired electrons is `V^(2+) < Cr^(2+) < Fe^(2+) < Mn^(2+)`. Thus, this statement is **incorrect**.

### Conclusion:
- The correct statements are:
- Statement (iii) is correct.
- Statements (i), (ii), and (iv) are incorrect.

### Final Answer:
The correct order of properties stated in the question is:
- (iii) `Sc < Ti < Cr < Mn` : number of oxidation states