Ralph Pearson

Ralph G. Pearson ( born January 12, 1919 in Chicago) is an American chemist. He was known for his work in the field of theoretical inorganic chemistry. Since 1976 he has taught at the University of California, Santa Barbara.

HSAB concept

The HSAB concept, which introduced Pearson in the 1960s, explains that ion soft acids (large polarizability ) preferably connect ion soft bases. Ion of hard acids (low polarizability ) combine preferentially with hard bases ions.

Principle of maximum hardness

Pearson's principle of maximum hardness indicates that the most stable chemical compounds have a maximum energy gap between the HOMO and the LUMO. These are the compounds with the maximum chemical hardness. For example, the HOMO-LUMO energy gap in tetrahedral methane is much larger than the planar shape. The general applicability of this principle is questioned in the literature.

Honors

Pearson is a member of the National Academy of Sciences.

Works

• R. G. Pearson ( 1973). Hard and Soft Acids and Bases. Dowden, Hutchinson and Ross. ISBN 0-87933-021 -X
• R. G. Pearson ( 1997). Chemical Hardness. Wiley- VCH, Weinheim. ISBN 3-527-29482-1