PearsonHSABPrinzip
Pearson HSAB principle, named after Ralph G. Pearson, is a qualitative framework in chemistry used to rationalize and predict the outcome of many acid–base reactions. It classifies acids and bases as hard or soft and posits that hard acids prefer to bind hard bases, while soft acids prefer soft bases; interactions between hard and soft partners tend to be less favorable.
Hard species are small, highly charged, and poorly polarizable; soft species are larger, less charged, and highly
Quantitative aspects were developed by extending the idea with global hardness and softness from density functional
Examples include hard acid–hard base pairs such as Mg2+ with F− or H2O, and soft acid–soft base
Limitations include its status as a guideline rather than a universal law, with solvent effects, covalent character,