Nuclear Reactions and Radioactive Decay

In 1903, Rutherford and Frederick Soddy (1877–1956) proposed that radioactivity

is the result of a natural change of an isotope of one element into an isotope of a

different element. Such processes are called nuclear reactions.

Consider a reaction in which radium-226 (the isotope of radium with mass number

226) emits an particle to form radon-222. The equation for this reaction is

226

88Ra → 4

2 222

86Rn

In a nuclear reaction, the sum of the mass numbers of reacting particles must

equal the sum of the mass numbers of products. Furthermore, to maintain nuclear

charge balance, the sum of the atomic numbers of the products must equal the

sum of the atomic numbers of the reactants. These principles are illustrated using

the preceding nuclear equation:

226

88Ra → 4

2 222

86Rn

radium-226 → particle radon-222