Which element among d-block element has(i) the lowest melting point and (ii) the highest melting point

Answer

To determine which d-block element has the lowest and highest melting points, we need to analyze the metallic bonding and the number of unpaired electrons in these elements.

### Step-by-Step Solution:

1. **Understanding Metallic Bonding:**
- The melting point of metals is influenced by the strength of metallic bonding, which is determined by the number of unpaired valence electrons. More unpaired electrons lead to stronger metallic bonding and higher melting points.

2. **Identifying the Element with the Lowest Melting Point:**
- Among the d-block elements, mercury (Hg) has the lowest melting point.
- **Reason:** Mercury has the electronic configuration of [Xe] 4f14 5d10 6s2, meaning both the d and s orbitals are fully filled. This results in no unpaired electrons, leading to weaker metallic bonding. Consequently, mercury is a liquid at room temperature, with a melting point of approximately -38.83 °C.

3. **Identifying the Element with the Highest Melting Point:**
- Tungsten (W) has the highest melting point among the d-block elements.
- **Reason:** Tungsten has the electronic configuration of [Xe] 4f14 5d4 6s2, which means it has six unpaired electrons (four in the d orbital and two in the s orbital). The presence of multiple unpaired electrons enhances the metallic bonding, resulting in a very high melting point of about 3422 °C.

4. **Conclusion:**
- The element with the lowest melting point among the d-block elements is **mercury (Hg)**, and the element with the highest melting point is **tungsten (W)**.

### Summary:
- **Lowest Melting Point:** Mercury (Hg) - approximately -38.83 °C
- **Highest Melting Point:** Tungsten (W) - approximately 3422 °C