The Nobel Prize in Chemistry 1921 was awarded to Frederick Soddy "for his contributions to our knowledge of the chemistry of radioactive substances, and his investigations into the origin and nature of isotopes".
 

Frederick Soddy received his Nobel Prize one year later, in 1922. During the selection process in 1921, the Nobel Committee for Chemistry decided that none of the year's nominations met the criteria as outlined in the will of Alfred Nobel. According to the Nobel Foundation's statutes, the Nobel Prize can in such a case be reserved until the following year, and this statute was then applied. Frederick Soddy therefore received his Nobel Prize for 1921 one year later, in 1922.
 

Isotopes are nuclear configurations of atoms, with a specific number of neutrons and a specific elemental type. For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 respectively.