What are the four Hume-Rothery rules for the solid solubility of one element in another?

Answer 1

• If a solute differs in its atomic size by more than about 15% from the host, then it is likely to have a low solubility in that metal. The size factor is said to be unfavourable.
• If a solute has a large difference in electronegativity (or electropositivity) when compared with the host, then it is more likely to form a compound. Its solibility in the host would therefore be limited.
• A metal with a lower valency is more likely to dissolve in one which has a higher valency, than vice versa.

Answer 2

1. The atomic sizes of the solvent and solute elements should not differ by more than approximately 15%.
2. The same crystal structure must be shared by both solvent and solute.
3. Similar electronegativities between the solvent and solute elements are preferred.
4. The valence electrons should have similar characteristics between the solvent and solute.