Atomic change

Crookes discovered a method for treating uranium compounds in a way to make them much less radioactive. Uranium might not be radioactive after all. Becquerel suggested that this was due to a spontaneous change of one atom into another, the first suggestion of its kind.
 William Crookes England 1900 Atomic change

Crookes discovered a method for treating uranium compounds in a way to make them much less radioactive. Uranium might not be radioactive after all. Becquerel suggested that this was due to a spontaneous change of one atom into another, the first suggestion of its kind.