Introduction

Abstract

The discovery of isotopes dates back to the beginning of the century, when Boltwood (1907) found radioactive elements with the same chemical properties but different masses, and three kinds of radioactivity of which the α and β radiation had to be seen as charged particles, for it could be influenced by electrical fields. The occurrence of different masses at the same position of the periodic system, i.e. the same number of protons but different numbers of neutrons (which were discovered first in 1930) could be explained by the different results of radioactive decay. The emission of an α particle (now known as a heliumcore) shifted the resulting element two places to the left in the periodic system and, if β-decay then occurs twice (in this case the β ^-) the element was twice shifted back, reaching its original position again with a different number of neutrons (which were discovered after 1930). Soddy (1914) called these elements isotopes. Richards and Lembert (1914) found different atomic masses for Pb and Thomson (1914) separated the ion beams of neon in combined electric and magnetic fields, first proving the existence of isotopes of non radioactive atoms and establishing the principles of modern mass spectrometry.

Nature is but a name for an effect, Whose cause is god.

Willian Cowper, 1731–18000 (The task)