How was Frederick Soddy awarded the Noble Prize?

In 1904, Frederick Soddy was the University of Glasgow’s first lecturer in physical chemistry and radioactivity. He carried out a demanding series of experiments that established the relationship between atomic numbers and periodic table positions. His research led him to make the imaginative suggestion that elements with different atomic weights that did not seem separable by chemical means were indeed chemically identical. He proposed the term “isotope,” which means “equal place.” He won the 1921 Nobel Prize in Chemistry for his research on radioactive decay, particularly for formulating the isotope theory.