michael faraday was the first person to write a theory about ions, in 1830. in his theory, he said what the portions of molecules were like that moved to anions or cations. svante august arrhenius showed how this happened. he wrote this in his doctoral dissertation in 1884 (university of uppsala). the university did not accept his theory at first (he only just passed his degree). but in 1903, he won the nobel prize in chemistry for the same idea.