hard acid

hard acid

[′härd ′as·əd]
(chemistry)
A Lewis acid of low polarizability, small size, and high positive oxidation state; it does not have easily excitable outer electrons; some examples are H+, Li+, and Al+.
References in periodicals archive ?
According to Huheey, Keiter and Keiter (1997) [Cd.sup.2+] is considered a soft acid whereas [Zn.sup.2+] is a borderline one, which means that [Zn.sup.2+] is not a soft acid neither hard acid. Pearson (1963) affirms that the interaction between soft species is more polarizable than hard ones, and hard acids prefer to bind to hard acids, while soft acids prefer to bind to soft bases.
INA has two coordination sites; one is N which is suitable to coordinate to a soft acid metal (Cu) and the other is O which is suitable to coordinate with hard acid metal (Pr).