Frederick Soddy, at the University of Glasgow, coined in 1913 the term "isotope" (from Greek for "same place") to describe a phenomenon puzzling chemists of the time: different radioactive substances, with clearly different atomic masses, occupied exactly the same position in the periodic table and were chemically indistinguishable from one another. Soddy formulates the laws of radioactive displacement — developed in earlier collaboration with Ernest Rutherford on radioactive decay — establishing that when an atom emits an alpha particle it shifts two places back in the periodic table, and when it emits a beta particle it shifts one place forward. The concept of isotope resolves the contradiction by explaining that the same chemical element can exist in variants with different numbers of neutrons in the nucleus — and therefore different mass — without this affecting its chemical properties, which depend only on the number of protons. The discovery completely reorganizes the understanding of the periodic table and nuclear chemistry, and is fundamental to the later development of radiometric dating, nuclear medicine, and, decades later, uranium enrichment technology.