Among the first transition series (3d series) which has highest melting point. Why?

Options

A. V
B. Zn
C. Cu
D. Cr

Answer

To determine which element among the first transition series (3d series) has the highest melting point, we will analyze the melting points of the given elements: Vanadium (V), Chromium (Cr), Copper (Cu), and Zinc (Zn).

### Step-by-Step Solution:

1. **Identify the Electron Configurations:**
- Vanadium (V): Atomic number 23
- Electron configuration: [Ar] 3d³ 4s²
- Chromium (Cr): Atomic number 24
- Electron configuration: [Ar] 3d⁵ 4s¹ (notably, it has a half-filled d subshell)
- Copper (Cu): Atomic number 29
- Electron configuration: [Ar] 3d¹⁰ 4s¹ (fully filled d subshell)
- Zinc (Zn): Atomic number 30
- Electron configuration: [Ar] 3d¹⁰ 4s² (fully filled d subshell)

2. **Analyze the Melting Points:**
- The melting points of the elements are influenced by the number of unpaired electrons and the ability to form metallic bonds.
- Generally, elements with partially filled d orbitals can form stronger metallic bonds due to the presence of unpaired electrons.

3. **Compare the Elements:**
- Vanadium has 3 unpaired electrons in the d orbital.
- Chromium has 6 unpaired electrons (5 in the d orbital and 1 in the s orbital), which allows it to form multiple bonds.
- Copper and Zinc have completely filled d orbitals, which typically leads to lower melting points compared to elements with unpaired electrons.

4. **Conclusion:**
- Among the given options, Chromium (Cr) has the highest melting point due to its half-filled d orbital configuration, which allows it to form stronger metallic bonds compared to Vanadium, Copper, and Zinc.

### Final Answer:
**Chromium (Cr) has the highest melting point among the first transition series due to its half-filled d orbital, allowing for stronger metallic bonding.**