Alpha Beta Gamma

Lesson Contents 1.What is Radioactivity? 2.Physical properties of ,  and  3.Penetrating power of ,  and  4.N v Z  graphs (for fun) 5.Decay laws

Early Pioneers in Radioactivity Roentgen: Discoverer of X-rays 1895 Becquerel: Discoverer of Radioactivity 1896 The Curies: Discoverers of Radium and Polonium Rutherford: Discoverer Alpha and Beta rays 1897 Villard: Discovery of gamma rays

What do we mean by Radioactivity? Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. The general idea: An unstable nucleus releases energy to become more stable

Radioactivity – Is it a Health Problem? The Alpha, Beta and Gamma particles all add energy to the body’s tissues. It can alter DNA.

Alpha Radiation Alpha particles contain two protons and two neutrons

Alpha Radiation  has the same constitution as a Helium nucleus Alpha particles may be written as

Beta-minus Radiation Beta-minus particles are electrons

Beta-minus Radiation  - is produced when a neutron decays Beta-minus particles may be written as

Beta-minus Radiation  - is produced when a neutron decays The surplus mass is released as kinetic energy in the  - and as an antineutrino

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Gamma Radiation Gamma rays are a form of electro- magnetic radiation

Gamma Radiation  release is often associated with  or  decay Gamma rays remove energy from an unstable nucleus. Has no mass and no charge. O O

Penetrating power

N v Z graphs A Graph of neutron number (N) against proton number (Z) helps to predict whether an isotope will emit  or  - radiation

N v Z graphs Isotopes in this region emit  particles to become more stable. N decreases by 2 Z decreases by 2

N v Z graphs Isotopes in this region emit  particles to become more stable. N decreases by 1 Z increases by 1

Decay laws - alpha When an isotope emits an  particle  Its nucleon number decreases by 4  Its proton number decreases by 2 For example:

Decay laws – beta-minus When an isotope emits a  - particle  Its nucleon number is unchanged  Its proton number increases by 1 For example:

Decay laws Try writing the nuclear equations for the decay of these isotopes

Decay laws Answers

Stability is not usually achieved in a single step Stability is not usually achieved in a single step When a radioactive nucleus reaches a stable state by a series of steps, we call it a decay series When a radioactive nucleus reaches a stable state by a series of steps, we call it a decay series

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