http://www.ck12.org Chapter 11. Nuclear Chemistry
11.2 Radioactive Decay
Lesson Objectives
- Identify three types of radioactive decay.
- Define the half-life of a radioisotope.
- Explain radioactive dating.
Lesson Vocabulary
- half-life
- radioactive dating
- radioactive decay
Introduction
Unstable nuclei of radioisotopes become stable by emitting charged particles and energy. This process is called
radioactive decay. It is a nuclear, as opposed to chemical, reaction, in which one element changes into another.
Types of Radioactive Decay
There are three types of radioactive decay: alpha, beta, and gamma decay. In all three types, nuclei emit radiation,
but the nature of that radiation differs from one type of decay to another. You can watch a video about the three
types at this URL: http://www.youtube.com/watch?v=3koOwozY4oc (17:02).
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/680Alpha Decay
Alpha decay occurs when an unstable nucleus emits an alpha particle and energy. The diagram inFigure11.6
represents alpha decay. An alpha particle contains two protons and two neutrons, giving it a charge of +2. A helium
nucleus has two protons and two neutrons, so an alpha particle is represented in nuclear equations by the symbol