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Radioactive decay and nuclear radiation
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Unstable nuclei give out radiation to become more stable. The three types behave very differently.
Types of radiation
Nuclear equations
Alpha: mass number −4, atomic number −2.
Beta minus: a neutron becomes a proton: mass number unchanged, atomic number +1.
Gamma: no change to numbers; the nucleus loses energy.
Beta minus: a neutron becomes a proton: mass number unchanged, atomic number +1.
Gamma: no change to numbers; the nucleus loses energy.
Detecting radiation
A Geiger-Müller tube counts radiation. Photographic film darkens.
Background radiation is always present, from rocks, cosmic rays, food and medical sources.
Activity is measured in becquerels (Bq): decays per second.
Background radiation is always present, from rocks, cosmic rays, food and medical sources.
Activity is measured in becquerels (Bq): decays per second.
Radium-226 (atomic number 88) emits an alpha particle. What are the new mass number and atomic number?
- Mass number: 226 − 4 = 222
- Atomic number: 88 − 2 = 86
Answer: 222 and 86 (radon)
Alpha is a helium nucleus, stopped by paper, strongly ionising. Beta is a fast electron, stopped by aluminium. Gamma is EM radiation, reduced by lead. Alpha: mass −4, atomic −2. Beta: atomic +1.
The interactive lesson includes the diagrams for this topic.
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