In 1913, Soddy showed that an atom moves lower in atomic number by two places on alpha emission, higher by one place on beta emission. This was discovered at about the same time by Kazimierz Fajans, and is known as the radioactive displacement law of Fajans and Soddy, a fundamental step toward understanding the relationships among families of radioactive elements. In 1913 Soddy also described the phenomenon in which a radioactive element may have more than one atomic mass though the chemical properties are identical. He named this concept isotope meaning "same place". The word was initially suggested to him by Margaret Todd. Later, J. J. Thomson showed that non-radioactive elements can also have multiple isotopes.
In 1913 Soddy showed that an atom moves lower in atomic number by two places on alpha emission higher by one place on beta emission This was discovered at about the same time by Kazimierz Fajans and is known as the radioactive displacement law of Fajans and Soddy a fundamental step toward understanding the relationships among families of radioactive elements In 1913 Soddy also described the phenomenon in which a radioactive element may have more than one atomic mass though the chemical properties are identical He named this concept isotope meaning "same place" The word was initially suggested to him by Margaret Todd Later J J Thomson showed that non-radioactive elements can also have multiple isotopes