If two metals forming a substitutional solution have similar atomic size and the same crystal structure, which statement is true about the range of compositions that can form?

If two metals forming a substitutional solution have similar atomic size and the same crystal structure, which statement is true about the range of compositions that can form?

• A. They can form across complete range of compositions
• B. They can form only in small ranges
• C. They cannot form
• D. They require high temperatures

Answer: (D)

When two metals form a substitutional solid solution, atoms of one metal take the lattice sites of the other. If their atomic sizes are similar and they share the same crystal structure, the lattice can accommodate a wide variety of substitutions with minimal distortion. That compatibility allows the two metals to mix in any proportion and still form a single solid solution phase, giving a complete range of compositions. Temperature influences diffusion and the exact solubility limits, but the key factor driving a broad composition range is how closely the atoms fit into the lattice. Therefore, the statement that they can form across the complete range of compositions is the best answer. The idea that high temperatures are required isn’t a defining rule for achieving wide solubility, even though heating can facilitate mixing.

When two metals form a substitutional solid solution, atoms of one metal take the lattice sites of the other. If their atomic sizes are similar and they share the same crystal structure, the lattice can accommodate a wide variety of substitutions with minimal distortion. That compatibility allows the two metals to mix in any proportion and still form a single solid solution phase, giving a complete range of compositions.

Temperature influences diffusion and the exact solubility limits, but the key factor driving a broad composition range is how closely the atoms fit into the lattice. Therefore, the statement that they can form across the complete range of compositions is the best answer. The idea that high temperatures are required isn’t a defining rule for achieving wide solubility, even though heating can facilitate mixing.