ABSTRACT
Atomistic philosophy and early atomic theory postulate that atoms are the smallest particles of matter, which are both indivisible and eternal. The discovery of electrons, protons, and neutrons showed that atoms are, in fact, divisible into smaller particles. Coincident with the discovery of the electron, and itself key to the discovery of the proton and neutron, was the discovery of radioactivity. Radioactivity is the transmutation of an unstable, radioactive atomic nucleus into a new, more stable atomic nucleus. In this chapter, the causes of and types of radioactive decay (α, β, and γ) are investigated. The chapter concludes with an investigation of radioactive decay chains as a tool to understand both half-lives and the challenge that radioactive materials present to storage and disposal.
