Radioactivity and the Atomic Nucleus

Abstract

In 1896 Henri Becquerel discovered that compounds containing uranium emit radiations that can penetrate opaque paper and even thin sheets of metal and cause photographic plates to darken. Like x-rays, these emissions ionized air and caused electroscopes to discharge, but unlike x-rays, they occurred without any external source of excitation. Becquerel’s student, Marie Curie, named this spontaneous emission of ionizing radiation “radioactivity.”