Radiation and Radioactive Decay

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Radiation andRadioactive Decay

• Section 4.4 Notes and Sections 25.1-25.2

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In a Chemical Reaction

• changes occur to the electrons outside nucleus
• no change occurs in the nucleus
• elements involved dont change
• elements just rearrange themselves to form new
  compounds
• Example 2 H2 O2 ? 2 H2O

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In Nuclear Reactions . . .

• Changes occur in nucleus to number of n0 and p.
• n0 and p are collectively known as nucleons
• An unstable atoms nucleus radioactively decays
  into a different, more stable atoms nucleus.
• Example U-238 ? Th-90
• This is called transmutation!
• - radioactive decay process of an unstable
  nucleus emitting radiation to become a different,
  more stable nucleus

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In Nuclear Reactions . . .

• radiation includes energy as well as particles
  which are emitted from a radioactive material
• Radioisotopes undergo radioactive decay and emit
  radiation most often
  in a series of nuclear reactions
  called a radioactive decay series.

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Discovery of Types of Radiation
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Types of Radiation

• Alpha Particles (abbreviated ? )
• a positively charged particle
• composed of 2 protons and 2 neutrons which is the
  nucleus of a helium atom
• represented by the short-hand notation
• large mass relative to size so it moves slowly
• low penetration ability through materials because
  it moves so slowly
• can be blocked by thin, outer layer of our skin
  and paper

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Types of Radiation

• Beta Particles (abbreviated ß- )
• a negatively charged particle
• composed of a negatively charged electron
• represented by the short-hand - notation

• small mass relative to size so it moves fast
• greater penetration ability than alpha particles
  because they move faster because of their much
  smaller mass
• can be blocked by metals and protective clothing

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Types of Radiation

• Gamma Rays (abbreviated ? )
• neutral (no charge)
• composed of little bundles/packets of energy
  called photons
• represented by the short-hand notation
• usually emitted with ? and ? particles
• no mass so it travels at speed of light
• greatest penetration ability because they move at
  speed of light because of their zero mass
• can be blocked (but not fully) by lead, really
  thick concrete

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Radiation Particles and Their Penetration Power
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Geiger Counter

• Equipment used to detect radiation by listening
  to audible clicks.

Geiger Counter
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• Summarize what you just learned! ?

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What makes an atoms nucleus UNSTABLE?

• Stability depends on ratio of n0p
• The more p a nucleus gets, the more n0 it needs
  to balance out the electrostatic repulsion of p.
• Too many n0 and p makes the nucleus
  overcrowded like too many people on
  an elevator.
• So just like if an elevator is overcrowded,
  people have to get off, when a nucleus is
  overcrowded particles must be emitted this is
  radiation!

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Nuclear Equations
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Nuclear Equations
Numbers must balance!! Law of Conservation of
Matter must still be obeyed!
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Nuclear Equations

• Beta Emission

• Positron Emission

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Nuclear Equations

• Electron Capture

Gamma Emission usually accompanies other types
of decay. Transmutation one element becomes
another.
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We did it!!!