Radioactive Decay

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Radioactive Decay
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1896 Becquerel discovers natural radioactivity
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Marie Pierre Curie
Discovered radium and polonium.
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Types of Radioactive Decay
a alpha positively charged
ß beta negatively charged
? gamma neutral
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Alpha Particle

• A nucleus of a helium atom

2 protons and 2 neutrons
4 He 2
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Beta Particle

• An electron emitted from the nucleus

0 e -1
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Gamma Ray

• High frequency electromagnetic radiation

no mass and no charge
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Radiation in a Magnetic Field
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S
N
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Radiation Penetrating Power
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Alpha Decay

• radium-226 is an alpha emitter

226 4 222 Ra ? He
Rn 88 2 86
222 4 218 Rn ? He
Po 86 2 84
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Disintegration Energy (Q)
A ? B C Q
Q (mA (mB mC)) c2
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Polonium-218 is also an alpha emitter. What is
the daughter nuclide?
lead-214
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Beta Decay

• lead-214 is a beta emitter

_ ?
214 0 214 Pb ? e
Bi 82 -1 83
_ ? antineutrino
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beta decay of bismuth-214
214 0 214 _ Bi ?
e Po ? 83 -1 84
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Transmutation change from one element
to another
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19 19 10 Ne ? 9 F
0 1 e
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ß decay (positron emission)
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Gamma Radiation
excited state
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Nuclear Stability

• For light elements (Z 20), stable nuclide
• when n p or n p 1

For heavier elements (Z gt 20), need more
neutrons to overcome repulsions of protons.
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All isotopes heavier than Bi-209 (Zgt83) are
radioactive because proton-proton repulsions are
too great.
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