“How can we know if how an element will dissolve in a metal?”
I don’t know about you but all of the different types of elements simply astounds me. Just to think that by changing only a single proton of an atom the entire set of properties can change drastically. What’s even more exciting is that these different properties mean that elements can also combine in a myriad of different ways, such as by dissolving. And not only this, but there are even different ways in which atoms can dissolve in one another, specifically by forming a substitutional solid or an interstitial solid. So how can we predict which will happen? Well, let’s think about substitutional solids for a moment. We know that in order for an atom to be on the same lattice in a material (the substitute in substitutional), it must be of similar size (around 15%), have a similar crystal structure, be of the same valency, and have similar electronegativity. And if we want the element to be interstitial, we know that the element must be smaller than the original by at least 15%, show similar valency, and have the same valency. After working with such patterns for many decades, materials scientists have decided to term these rules the Hume-Rothery rules.