Linus Pauling (1901–1994): Linus Pauling was an American chemist and peace activist who made profound contributions to the fields of quantum chemistry and biochemistry. Born in the early 20th century, Pauling’s work in molecular structure and bonding led to many breakthroughs in both theoretical and applied chemistry. He developed the concept of electronegativity and valence bond theory, crucial elements in the study of chemical bonding. His exploration into the nature of the chemical bond helped establish the field of molecular biology. His model of the alpha-helix and beta-sheet significantly impacted the study of biochemistry. Pauling was awarded two Nobel Prizes in Chemistry in 1954 for his work on the nature of the chemical bond and in 1962 for his efforts in advocating against nuclear weapons testing.