Theodore William Richards

Theodore William Richards (1868-1928), American chemist and Nobel laureate. In 1914, Richards became the first American chemist to win the Nobel Prize in chemistry, for his work on determining atomic weights.

Born in Germantown, Pennsylvania, Richards received his elementary and secondary schooling at home and joined the sophomore class at Haverford College when he was 14. When he entered the senior class at Harvard University he was the youngest member, but graduated with highest honors earning his B.A. degree in chemistry in 1886. In 1901 Richards became a full professor at Harvard, and taught and did research there for his entire career.

Richards's best-known contribution to chemistry was in the field of atomic weight. An element's atomic weight is determined by comparing it to carbon. The atomic weight of one atom of carbon is 12 atomic mass units, or amu. Hydrogen, the smallest element has an atomic weight of 1 amu, while uranium has an atomic weight of 238 amu. When Richards began his work on atomic weights, the accepted periodic table (the listing of elements according to their atomic weight) was based upon a series of numbers set down in the 1860s and never questioned. Richards questioned the long-established numbers because he realized that they had been derived from studies that had let impurities slip into the samples of the elements. Richards redefined the atomic weights of 25 elements, work that produced significant changes in the accepted values for all elements.

Richards's other major contribution to the field of atomic weights was a comprehensive study that confirmed that the lead from radioactive minerals does have a different atomic weight from normal lead.

Although best known for his atomic weight studies, Richards also conducted research programs in thermochemistry and electrochemistry. Theorizing that an atom has a changeable volume that depends on its chemical state, Richards spent much of his later life unsuccessfully trying to correlate compressibilities of substances with their densities, surface tensions, heats of reaction, and other properties.