Apart from their radioactivity and high atomic weight, uranium, thorium, and radium show no specially distinctive chemical behaviour. Radium for example is closely allied in general chemical properties to barium. It is consequently not unreasonable to suppose that other elements may be built up in part of helium, although the absence of radioactivity may prevent us from obtaining any definite proof. On this view, it may prove significant that the atomic weights of many elements differ by four—the atomic weight of helium—or a multiple of four. Time is too limited to discuss in greater detail these and other interesting questions which have been raised by the proof of the chemical nature of the α-particle.
[1]E. Rutherford, Uranium radiation and the electrical conduction produced by it, Phil. Mag., 47 (1899) 116.
[2]E. Rutherford and F. Soddy, Phil. Mag., 5 (1903), 106.
[3]E. Rutherford and F. Soddy, Phil. Mag., 4 (1902), 582.
[4]E. Rutherford and F. Soddy, Phil. Mag., 5 (1903), 453.
[5]E. Rutherford, letter in Nature, 69 (Aug. 20, 1903).