Question

Why Cr has higher melting point than Mn ?

Hint:

Metallic bond strength \(\propto\) number of unpaired electrons participating in the bond. The stable \(d^5\) shell of Mn makes it an anomaly in the melting point trend.

Answer 1

Step 1: Understanding the Concept:
Melting point in transition metals depends on the strength of metallic bonds, which is directly related to the number of unpaired d-electrons available for delocalization.
Step 2: Detailed Explanation:
1. Chromium (\(Cr\)): It has a \(3d^5 4s^1\) configuration. It has 6 unpaired electrons that participate effectively in metallic bonding, leading to strong interatomic forces and a high melting point.
2. Manganese (\(Mn\)): It has a \(3d^5 4s^2\) configuration. Although it has 5 unpaired electrons in the 3d subshell, these electrons are held very tightly in the stable, symmetrical half-filled configuration. As a result, they participate less in metallic bonding, leading to weaker interatomic forces and a lower melting point compared to Chromium.
Step 3: Final Answer:
\(Cr\) has more effectively involved delocalized electrons than \(Mn\), leading to higher melting point.