Chapter 9 10/11/2012
9.1 Natural Radioactivity
Stable and Radioactive Isotopes
A radioactive isotope
• has an unstable nucleus
• emits radiation to become more stable, changing the composition of the nucleus
• is identified by the mass number of the isotope
Nuclear radiation is the radiation emitted by an unstable atom and takes the form of alpha particles,
neutrons, beta particles, positrons, or gamma rays.
Types of Radiation
Alpha (α) particle is two protons and two neutrons. 4 He
Beta (β) particle is a highenergy electron.
Positron (β+) is a positive electron. 0
+ 1 e
Gamma rays are the highenergy radiation released from a nucleus when it decays.
Radiation protection requires
• paper and clothing for alpha particles
• a lab coat or gloves for beta particles
• a lead shield or a thick concrete wall for gamma rays
• limiting the amount of time spent near a radioactive source
• increasing distance from the source
9.2 Nuclear Equations Balancing Nuclear Equations
In a balanced nuclear equation, particles are emitted from the nucleus, and
• the mass number a