Union 3, Lesson 3
Lesson 3 - Isotopes and Radioactivity
Student Performance Objectives
1. Define nuclear decay, nuclear stability and half-life.
2. Draw the Bohr models for hydrogen, deuterium and tritium.
3. Define biological half-life and background radiation.
4. Explain the difference in ionizing radiation exposure when a simple x-ray, an angiogram or
magnetic resonance imaging (MRI) is used in a medical imaging procedure.
A. Concept of ionizing radiation, sources and atomic nuclear stability.
1. Nuclear decay
2. Medical applications. See
B. Diagram hydrogen, deuterium and tritium.
C. Radioisotopes and half-life.
1. Physical half-life - time for 50% of atoms to decay to more stable
2. Biological half-life - time for half to disappear from the human body
generally through excretion.
D. Practical considerations
1. Background radiation from the sun and outer space.
2. Medical sources from dental and chest X-rays, CT scans.
3. Compare ionizing radiation to MRI's, sonograms, and thermograms.
4. Consider angiograms - one such motion picture X-ray procedure exposes one to the
equivalent of thousands of chest X-rays.