Question

The correct order of melting points of Al, Ga, In is:

• A. \( \text{Ga}<\text{In}<\text{Al} \)
• B. \( \text{In}<\text{Ga}<\text{Al} \)
• C. \( \text{Al}<\text{Ga}<\text{In} \)
• D. \( \text{Ga}<\text{Al}<\text{In} \)

Hint:

When comparing the melting points of metals in the same group, the trend generally increases as the atomic size decreases due to stronger metallic bonds.

Answer 1

The Correct Option is A

The melting points of Al, Ga, and In are governed by their atomic structure and bonding characteristics. Based on the trends in metallic bonding: - \( \text{Ga} \) (Gallium) has the lowest melting point among the three elements, primarily because of weaker metallic bonds and a relatively low atomic number. - \( \text{In} \) (Indium) has a slightly higher melting point than Ga due to its larger atomic size and stronger metallic bonds. - \( \text{Al} \) (Aluminum) has the highest melting point because it exhibits stronger metallic bonding due to its smaller atomic size and higher charge density. Thus, the correct order is \( \text{Ga}<\text{In}<\text{Al} \).

Answer 2

Step 1: Understanding the Metals Involved
Aluminum (Al), Gallium (Ga), and Indium (In) are group 13 elements. Their melting points depend on their atomic structure and bonding forces between atoms.

Step 2: Atomic Structure and Bonding
Aluminum has a strong metallic bonding due to its small atomic size and high charge density, resulting in a high melting point.

Gallium has an unusual low melting point because it forms covalent-like dimers (Ga₂) in the solid state, which weakens the metallic bonding.

Indium has larger atomic size and weaker metallic bonding than aluminum but stronger than gallium, giving it a melting point between Ga and Al.

Step 3: Comparing Melting Points
Due to these factors, the melting points increase in the order:
Ga < In < Al

Step 4: Conclusion
Hence, the correct order of melting points is gallium less than indium less than aluminum.