All chemistry students today know about isotopes, which are atoms of the same element with identical chemical properties but different atomic weights. However, few people know where the name comes from.
Margaret Todd wasn’t a research scientist, but she did have medical qualifications. Todd was also a friend of English radiochemist Frederick Soddy (1877-1956), who worked with Ernest Rutherford and contributed much to chemistry as a field. In 1921, he was awarded the Nobel Prize in Chemistry.
In conversation with Soddy, Todd proposed the name “isotope.” The term is derived from the Greek phrase isos topos, which means “same place.” With this name, Todd emphasized the idea that these slightly different versions of an element should all be in the same place in the periodic table, which supported the concept that the fundamental property driving chemical periodicity wasn’t atomic weight but rather atomic number.
Todd’s role in the introduction of the term “isotope” remained unknown for over 30 years.