Why do animal cells "mistake" rubidium ions for potassium ions? includes the following passage:
In the case of potassium versus sodium, which are both very important in biochemistry, a recently discovered mechanism in sodium-potassium pumps uses binding properties to grab both, then atomic size (via steric hindrance) to distinguish sodium versus potassium as described nicely in the answers to this question.
Wikipedia's Steric effects says:
Steric effects are nonbonding interactions that influence the shape (conformation) and reactivity of ions and molecules. Steric effects complement electronic effects, which dictate the shape and reactivity of molecules. Steric repulsive forces between overlapping electron clouds result in structured groupings of molecules stabilized by the way that opposites attract and like charges repel.
Since ""the way that opposites attract and like charges repel"" sounds ""electronic"" to me, why does one say that ""Steric effects complement electronic effects"" instead of simply being electronic effects?"