The melting point of copper is higher than that of zinc because

The ‘s’ as well as ‘d’ electrons of copper are involved in metallic bonding

The correct answer is option 4. The ‘s’ as well as ‘d’ electrons of copper are involved in metallic bonding.

The melting point of copper (Cu) is higher than that of zinc (Zn) primarily because the 's' as well as 'd' electrons of copper are involved in metallic bonding.

Let us look at the various fators:

Metallic Bonding: Metallic bonding occurs between metal atoms where valence electrons are delocalized and free to move throughout the solid. In copper, both the 's' electrons (from the outermost shell) and the 'd' electrons (from the d-orbitals) contribute to metallic bonding. These electrons are loosely bound and can move freely within the lattice of copper atoms, contributing to strong metallic bonds.

Comparison with Zinc:

Zinc has a lower melting point compared to copper. Zinc primarily utilizes its 's' electrons for metallic bonding, which are less shielded from the nuclear charge compared to copper's 's' and 'd' electrons. The involvement of both 's' and 'd' electrons in copper enhances the strength of metallic bonding, leading to stronger interatomic forces and a higher melting point.

Other Factors:

Crystal Structure: Copper has an FCC (face-centered cubic) crystal structure, which generally contributes to higher melting points compared to metals with simpler crystal structures like HCP (hexagonal close-packed) as in zinc.

Atomic Volume: While atomic volume can influence melting points, it is not the primary reason for the higher melting point of copper over zinc. Copper's crystal structure and the involvement of 'd' electrons play more significant roles.

Conclusion: Therefore, the correct reason why the melting point of copper is higher than that of zinc is because the 's' as well as 'd' electrons of copper are involved in metallic bonding, which enhances the strength of interatomic forces and thus increases the melting point of copper.