Which of the following is arranged in order of increasing melting point?

Options

A. `ZnltCu ltNiltFe`
B. `FeltNiltCu ltZn`
C. `NiltFeltZnltCu`
D. `Cu ltZnltFeltNi`

Answer

To solve the problem of arranging the transition metals in order of increasing melting point, we will follow these steps:

### Step 1: Identify the Transition Metals
We need to identify which transition metals are given in the question. For this solution, let's assume the metals are Iron (Fe), Copper (Cu), Nickel (Ni), and Zinc (Zn).

### Step 2: Determine the Electron Configuration
Next, we will write the electron configuration for each of the metals to find the number of unpaired electrons:
- **Iron (Fe)**: [Ar] 4s² 3d⁶
- **Copper (Cu)**: [Ar] 4s² 3d⁹
- **Nickel (Ni)**: [Ar] 4s² 3d⁸
- **Zinc (Zn)**: [Ar] 4s² 3d¹⁰

### Step 3: Count the Number of Unpaired Electrons
Now, we will determine the number of unpaired electrons for each metal:
- **Iron (Fe)**: 4 unpaired electrons (3d⁶)
- **Copper (Cu)**: 1 unpaired electron (3d⁹)
- **Nickel (Ni)**: 2 unpaired electrons (3d⁸)
- **Zinc (Zn)**: 0 unpaired electrons (3d¹⁰)

### Step 4: Relate Unpaired Electrons to Melting Point
The melting point of transition metals is directly proportional to the number of unpaired electrons. Therefore, the more unpaired electrons a metal has, the higher its melting point.

### Step 5: Arrange Metals by Melting Point
Based on the number of unpaired electrons, we can arrange the metals in order of increasing melting point:
1. **Zinc (Zn)**: 0 unpaired electrons
2. **Copper (Cu)**: 1 unpaired electron
3. **Nickel (Ni)**: 2 unpaired electrons
4. **Iron (Fe)**: 4 unpaired electrons

### Final Answer
The order of increasing melting point is:
**Zn < Cu < Ni < Fe**