Which English radiochemist explained radioactive transmutation with Ernest Rutherford?

Frederick Soddy explained radioactive transmutation with Ernest Rutherford.

Working at McGill University from 1900 to 1903, Soddy and Rutherford investigated the strange emissions from radioactive substances. Their work showed that radioactivity was not merely energy escaping from unchanged atoms: radioactive atoms could spontaneously disintegrate and become atoms of other elements.

This overturned the long-standing view that chemical elements were immutable. Their 1902–1903 work led to the law of radioactive change and helped establish the foundations of radiochemistry and nuclear physics. Soddy later developed the concept of isotopes and received the 1921 Nobel Prize in Chemistry.

A common mix-up is with William Ramsay, who worked with Soddy in 1903 to demonstrate helium from radium decay. Ramsay was an important collaborator in that experiment, but Soddy was the radiochemist associated with explaining transmutation alongside Rutherford.