Which is the stronger lewis acid Cu+ or Cu2+?
Given the definition of
This can also be explained via HSAB theory.
A harder acid holds onto its electron density more than a softer acid. The hardness of a lewis acid increases with increasing positive charge, as the electron density is more concentrated.
#"Cu"^(2+)#is the harder acid, being less polarizable than a softer acid.
That means it accepts electron density more easily, because it holds onto it more easily (it is less polarizable), and consequently has greater polarizing ability (can distort other electron clouds more easily than a softer acid can).
#bb("Cu"^(2+))#is the stronger Lewis acid.