http://www.ck12.org Chapter 24. Nuclear Chemistry
24.2 Half-Life
Lesson Objectives
- Define half-life as it relates to radioactive nuclides and solve half-life problems.
- Describe the general process by which radioactive dating is used to determine the age of various objects.
- Explain the mechanism of a decay series.
- Define and write equations for artificial transmutation processes.
Lesson Vocabulary
- artificial transmutation
- decay series
- half-life
- radioactive dating
Check Your Understanding
Recalling Prior Knowledge
- Kinetics is the study of what aspect of chemical reactions?
- What must be balanced in an equation for a nuclear reaction?
The rate of radioactive decay is different for every radioisotope. Less stable nuclei decay at a faster rate than more
stable nuclei. In this lesson, you will learn about the half-lives of radioactive nuclei.
Half-Life
The rate of radioactive decay is often characterized by the half-life of a radioisotope. Half-life (t 12 )is the time
required for one half of the nuclei in a sample of radioactive material to decay. After each half-life has passed,
one half of the radioactive nuclei will have transformed into a new nuclide (Table24.3). The rate of decay and the
half-life does not depend on the original size of the sample. It also does not depend upon environmental factors such
as temperature and pressure.
TABLE24.3:Half life
Number of Half-Lives Passed Percentage of Radioisotope Remaining
1 50