Linus Pauling

Linus Carl Pauling was an American chemist, biochemist, engineer, educator and peace activist whose work helped establish modern quantum chemistry and molecular biology. Over a career spanning more than six decades, he published more than twelve hundred papers and books, making him one of the most prolific scientists of the twentieth century. His pioneering research on the nature of the chemical bond, the structure of molecules and the behaviour of proteins earned him international recognition, while his later involvement in peace and humanitarian causes established him as one of the most prominent scientific voices of his time. Pauling remains one of the very few individuals to have received two Nobel Prizes and the only person ever awarded two unshared Nobels—Chemistry in 1954 and Peace in 1962.
His scientific achievements included the formulation of the concept of orbital hybridisation, the first widely accepted scale of electronegativity and the identification of fundamental secondary structures in proteins, particularly the alpha helix and beta sheet. Using an approach that blended quantum mechanics, X-ray crystallography and molecular model building, Pauling contributed directly to the intellectual groundwork that enabled the later discovery of the DNA double helix. Alongside his scholarly work, he became known for his public advocacy, opposing nuclear weapons testing and later promoting orthomolecular medicine, though his medical claims regarding high-dose vitamin therapy were not adopted by mainstream science.

Early Life and Education

Pauling was born in Portland, Oregon, in 1901, the eldest child of Herman Henry William Pauling and Lucy Isabelle Darling. His family moved frequently across Oregon during his childhood as his father sought stable employment, eventually settling for periods in towns such as Oswego, Salem and Condon. His father died in 1910, leaving his mother to support the family. Pauling credited his early interest in chemistry to experiments he observed in a small home laboratory belonging to a friend and to his own early attempts at chemical investigations using salvaged materials.
Despite financial constraints, he proved an outstanding student. He entered Oregon Agricultural College (now Oregon State University) in 1917 without having completed a high-school diploma, a formality that was granted to him retrospectively many years later. As an undergraduate he undertook extensive coursework in chemistry, mathematics, engineering and related subjects, while supporting himself through part-time work and teaching positions. Fascinated by recent developments in atomic theory, he resolved to study the relationship between atomic structure and the properties of matter, a decision that would set the direction of his later research.
He graduated in 1922 with a degree in chemical engineering and enrolled at the California Institute of Technology (Caltech) for doctoral study. Under the guidance of Roscoe Dickinson and Richard Tolman, he applied X-ray diffraction to determine crystal structures, publishing several papers on minerals. He earned his PhD in 1925 with distinction.

Formation of Quantum Chemistry

Awarded a Guggenheim Fellowship, Pauling spent 1926–1927 in Europe, studying with Arnold Sommerfeld in Munich, Niels Bohr in Copenhagen and Erwin Schrödinger in Zürich. Exposure to the newly developing field of quantum mechanics inspired him to apply the new physics to chemical problems, particularly electron configuration and molecular bonding. He studied the pioneering work of Heitler and London on the hydrogen molecule and decided to focus his career on the quantum mechanical interpretation of chemical structure.
Returning to Caltech as a faculty member in 1927, he rapidly became a central figure in the development of quantum chemistry. He combined theoretical calculations with structural studies using X-ray crystallography, publishing extensively and formulating rules about ionic structures that later became known as Pauling’s rules. By the end of the 1920s he had been promoted to associate professor, and soon thereafter to full professor, marking the beginning of an extraordinarily productive period.

Contributions to Structural Chemistry and Molecular Biology

Pauling’s most influential scientific work concerned the nature of the chemical bond. His book The Nature of the Chemical Bond, published in 1939, became one of the most important chemistry texts of the twentieth century. He introduced concepts such as hybrid orbitals and created the first quantitative electronegativity scale, providing a framework for predicting the behaviour of atoms in molecules.
From the 1930s onward he collaborated with crystallographers and biochemists to explore the architecture of proteins. By building physical molecular models and applying principles of quantum chemistry, he elucidated how polypeptide chains could fold into stable structures. His identification of the alpha helix and beta sheet revolutionised the understanding of protein secondary structure and laid the foundation for modern structural biology. This body of work influenced the investigations of those attempting to determine the structure of DNA.
In later years he turned to medical chemistry and proposed orthomolecular approaches to health, especially the use of high doses of vitamins. Although these ideas became influential in popular culture, they were not accepted by the medical research community due to insufficient evidence.

Peace Activism and Public Engagement

During the 1950s Pauling emerged as a leading advocate for nuclear disarmament. He campaigned vigorously against atmospheric nuclear testing, citing genetic and environmental dangers. His activism culminated in the submission of a petition to the United Nations endorsed by thousands of scientists. The Nobel Peace Prize awarded to him in 1962 recognised his efforts in promoting the Partial Test Ban Treaty and raising public awareness of nuclear risks.
Beyond his political work, Pauling was an engaging educator, author and public figure. He lectured widely, contributed to science popularisation and collaborated with his wife, Ava Helen Pauling, who was active in social and humanitarian causes.

Legacy and Influence

Pauling’s influence on chemistry and biology remains profound. His integration of physical principles with chemical behaviour helped establish quantum chemistry as a discipline, and his insights into molecular structure underpin much of contemporary biochemistry and materials science. The electronegativity scale he devised continues to serve as a fundamental tool in understanding chemical reactivity.
His awards, publications and the breadth of his research attest to an extraordinary scientific career, while his peace activism illustrates the broader responsibilities he believed scientists should bear. Despite controversies surrounding some of his later medical claims, he remains one of the most significant scientific figures of the modern era.