One of the twentieth century's greatest chemists, Linus Pauling was born in Portland, Oregon, on February 28, 1901. He became interested in chemistry early in life as a result of his work with a home chemistry set, earning a bachelor's degree in chemistry from Oregon State College (now University) in 1922 and a doctorate in physical chemistry from California Institute of Technology in 1925. During post-doctoral studies in Europe, Pauling worked with some of the most famous chemists and physicists of the time, Erwin Schrödinger in Zurich, Niels Bohr in Copenhagen, William Henry Bragg (l862-l942) in London, and Arnold Sommerfeld in Münich.
Some of Pauling's earliest work dealt with the structure of molecules. Molecular models of the 1920s generally assumed that chemical bonding occurred between stable electrons. Gilbert Newton Lewis, for example, drew valence electrons in an atom at the corners of a cube. Bonds formed when two cubic atoms got close enough to allow overlap of corners. Pauling recognized that a more accurate way to think of electrons was as particles moving through space in a wave pattern.
Louis Victor de Broglie had formulated the mathematics needed to describe such " electron waves" in 1923. Pauling showed how the wave patterns for electrons in two atoms might overlap to produce a new hybrid pattern that was less energetic and, therefore, more stable than either of the original wave patterns. This discovery provided the first rational explanation of chemical bond formation. A second consequence of Pauling's work was the theory of resonance. In some cases, the bonds in a molecule do not display the properties of a pure single bond or a pure double bond, but instead act as some type of intermediary structure. Pauling demonstrated that this behavior could be explained by the assumption that the electrons making up the bond resonate back and forth between two extreme positions. Yet a third implication of Pauling's analysis was the discovery that most chemical bonds are not, as had been supposed, purely ionic or purely covalent. Instead of thinking in terms of the complete loss or gain of electrons or the equal sharing of electron pairs, Pauling suggested that most bonds have a mixed character best described as polar covalent. That is, the pair of electrons shared between two atoms is more strongly attracted by one of the atoms than by the other. Pure ionic and pure covalent bonds, then, become only the extreme cases of polar bonds when one atom "wins" both electrons completely or when the two atoms share electrons equally. Pauling outlined his analysis of bonding in his influential book, The Nature of the Chemical Bond, in 1939.
In the 1930s, Pauling had become increasingly interested in the molecular structure of complex biological substances and studied the properties of the hemoglobin molecule and its role in the genetic disorder known as sickle-cell anemia. In the early 1950s, he and chemist Robert Corey demonstrated the helical structure of protein. After World War II, Pauling became concerned about the global implications of nuclear weapons testing. In 1958, he published those concerns in a book entitled No More War! and brought to the United Nations a petition bearing the names of more than eleven thousand scientists, asking for an end to nuclear weapons testing. Pauling was awarded the Nobel Prize in Chemistry in 1954 for his work on the chemical bond and in 1962 he won the Nobel Prize for Peace for his work on nuclear weapons testing. He taught at California Institute of Technology from 1927 until his retirement in 1958.
Later in his career Pauling became well known for his controversial claim that ascorbic acid-- vitamin C--helps combat colds and disease. He outlined his findings in the l970 book Vitamin C and the Common Cold, focusing in a later book on vitamin C and cancer. He has served as a professor emeritus at Stanford University beginning in l974. Before his death in 1994 Pauling was a member of the Center for the Study of Democratic Institutions, a faculty member of Stanford University, and director fo research at the Linus Pauling Institute of Science and Medicine in Palo Alto, California.
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