Natural Radioactivity

In the late 19th century, while studying radiation emanating from uranium and

thorium, Ernest Rutherford (1871–1937) stated, “There are present at least two

distinct types of radiation—one that is readily absorbed, which will be termed for

convenience (alpha) radiation, and the other of a more penetrative character,

which will be termed (beta) radiation.” Subsequently, charge-to-mass ratio measurements

showed that radiation is composed of helium nuclei (He2 ) and

radiation is composed of electrons (e ) (Table 23.1).

Rutherford hedged his bet when he said at least two types of radiation existed.

A third type was later discovered by the French scientist Paul Villard (1860–1934);