In 1901 and 1902 he worked with Frederick Soddy to prove that atoms of one radioactive element would spontaneously turn into another, by expelling a piece of the atom at high velocity. Many ...

Some substances, like particles of this iron, contain only one kind of atom. Iron is an element. It is made of only one type of atom: iron atoms. Sulfur is another element. It contains only sulfur ...

Thus when an atom absorbs or gives off energy (as in light ... was the key to the periodic repetition of properties of the elements. The shells in which electrons orbit have different quantum ...