Hume Rothery Rules

Question 1

First Rule

Answer 1

Size factor.

If a solute differs in atomic size by more than about 15% from the host, then it is likely to have low solubility in that metal.

Question 2

Second Rule

Answer 2

Electronegativity.

If solute has a large difference in electronegativity (or electropositivity) when compared to the host, then it is more likely to form a compound, meaning its solubility would be limited.

Question 3

Third Rule

Answer 3

Valency.

A metal with a lower valency is more likely to dissolve in one which has a higher vacancy, than vice versa.