Ralph Pearson
Encyclopedia
Ralph G. Pearson is a physical inorganic chemist
best known for the development of the concept of hard and soft acids and bases (HSAB).
He received his Ph.D. in physical chemistry in 1943 from Northwestern University
, and taught chemistry at Northwestern faculty from 1946 until 1976, when he moved to University of California at Santa Barbara (UCSB). He retired in 1989 but remains active in research in theoretical inorganic chemistry.
In 1963 he proposed the qualitative theory of hard and soft acids and bases (HSAB) in an attempt to unify the theories of reactivity in inorganic and organic chemistry. In this theory 'Hard' applies to species that are small, have high charge states, and are weakly polarizable
. 'Soft' applies to species that are large, have low charge states and are strongly polarizable. Acids and bases interact, and the most stable interactions are hard-hard and soft-soft.
In 1967 Pearson and Fred Basolo
, his colleague at Northwestern wrote the influential monograph "Mechanisms of Inorganic Reactions", which integrated concepts from ligand field theory
and physical organic chemistry
and signaled a shift from descriptive coordination chemistry to a more quantitative science.
In 1983 in collaboration with Robert Parr
, he refined the HSAB theory into a quantitative method by calculating values of “absolute hardness” using density functional theory
, an approximate method in molecular quantum mechanics.
Inorganic chemistry
Inorganic chemistry is the branch of chemistry concerned with the properties and behavior of inorganic compounds. This field covers all chemical compounds except the myriad organic compounds , which are the subjects of organic chemistry...
best known for the development of the concept of hard and soft acids and bases (HSAB).
He received his Ph.D. in physical chemistry in 1943 from Northwestern University
Northwestern University
Northwestern University is a private research university in Evanston and Chicago, Illinois, USA. Northwestern has eleven undergraduate, graduate, and professional schools offering 124 undergraduate degrees and 145 graduate and professional degrees....
, and taught chemistry at Northwestern faculty from 1946 until 1976, when he moved to University of California at Santa Barbara (UCSB). He retired in 1989 but remains active in research in theoretical inorganic chemistry.
In 1963 he proposed the qualitative theory of hard and soft acids and bases (HSAB) in an attempt to unify the theories of reactivity in inorganic and organic chemistry. In this theory 'Hard' applies to species that are small, have high charge states, and are weakly polarizable
Polarizability
Polarizability is the measure of the change in a molecule's electron distribution in response to an applied electric field, which can also be induced by electric interactions with solvents or ionic reagents. It is a property of matter...
. 'Soft' applies to species that are large, have low charge states and are strongly polarizable. Acids and bases interact, and the most stable interactions are hard-hard and soft-soft.
In 1967 Pearson and Fred Basolo
Fred Basolo
Fred Basolo was an American inorganic chemist. He received his Ph.D. at the University of Illinois at Urbana-Champaign in 1943 with John C. Bailar. Basolo spent his entire professional career at Northwestern University...
, his colleague at Northwestern wrote the influential monograph "Mechanisms of Inorganic Reactions", which integrated concepts from ligand field theory
Ligand field theory
Ligand field theory describes the bonding, orbital arrangement, and other characteristics of coordination complexes. It represents an application of molecular orbital theory to transition metal complexes. A transition metal ion has nine valence atomic orbitals, five d, one s, and three p orbitals...
and physical organic chemistry
Physical organic chemistry
Physical organic chemistry is the study of the interrelationships between structure and reactivity in organic molecules. It can be seen as the study of organic chemistry using tools of physical chemistry such as chemical equilibrium, chemical kinetics, thermochemistry, and quantum chemistry...
and signaled a shift from descriptive coordination chemistry to a more quantitative science.
In 1983 in collaboration with Robert Parr
Robert Parr
Robert Ghormley Parr is a theoretical chemist. He is a chemistry professor at the University of North Carolina at Chapel Hill.-Career:...
, he refined the HSAB theory into a quantitative method by calculating values of “absolute hardness” using density functional theory
Density functional theory
Density functional theory is a quantum mechanical modelling method used in physics and chemistry to investigate the electronic structure of many-body systems, in particular atoms, molecules, and the condensed phases. With this theory, the properties of a many-electron system can be determined by...
, an approximate method in molecular quantum mechanics.
Honours
- American Chemical SocietyAmerican Chemical SocietyThe American Chemical Society is a scientific society based in the United States that supports scientific inquiry in the field of chemistry. Founded in 1876 at New York University, the ACS currently has more than 161,000 members at all degree-levels and in all fields of chemistry, chemical...
Award for Distinguished Service to Inorganic Chemistry 1970 - Member of National Academy of Science 1974