Unstable Nuclei and Radioactive Decay

1. Unstable Nuclei and Radioactive Decay

2. Radioactivity (Radioactive decay) • The process by which some substances spontaneously emit radiation. • Radioactive atoms emit radiation because their nuclei are unstable. • This loss of energy (radiation) allows the unstable atoms to gain stability. • By emitting radiation, an unstable atom of one element changes into a stable atom of another element.

3. Types of Radiation • Scientists identified 3 types of radiation by applying an electric field to radiation from a radioactive source. • Figure 4.5 on page 124

4. Alpha Radiation • Deflected toward the negatively charged plate • Made of alpha particles • Each particle contains 2 protons and 2 neutrons • Has a 2+ charge • Equivalent to a helium-4 nucleus • Represented by α or • Nuclear equation =

5. Beta Radiation • Deflected toward the positively charged plate • Made of beta particles • Each particle is a fast moving electron • Has a 1- charge • Mass = Mass of electron (1/1840 amu) • Represented by β or • Nuclear equation =

6. Gamma Radiation • Accounts for most of the energy lost during radioactive decay • Not deflected by electric or magnetic charges • Made of massless high energy rays • Possess no electrical charge • Represented by γ • Nuclear equation = n + 6Li = 7Li +γ

7. Nuclear Stability • Primary factor in determining nuclear stability is the ratio of neutrons to protons. • An atom with too many or too few neutrons is unstable. • These atoms radioactively decay until they form stable atoms with appropriate neutron to proton ratios.