Radioactivity is defined as the spontaneous breaking up of certain unstable nuclei, accompanies by the emission of radiation
Radioactivity is detected by a Geiger-Muller tube.
α particles (alpha)
Alpha particles are helium nuclei with a positive charge and little penetrating energy
Alpha decay involves:
- 2 protons lost – atomic number -2
- 2 protons + 2 neutrons lost – mass number -4
- New element formed
β particles (beta)
Beta particles are electrons with a negative charde and greater penetrating ability than alpha particles
Beta decay involves:
- Neutron breaks up into 1 proton and 1 electron
- Proton stays – atomic number +1
- Neutron replaced by proton – mass number no change
- New element formed
γ rays (gamma)
Gamma rays are high energy electromagnetic radiation, with greater penetrating power than beta particles. Neutral charge.
- Gamma rays are a form of energy, not particles – no mass or charge
- No new element formed
- Energy emitted
Radioactive Reactions
Nuclear reactions cause elements to change into other elements – changes in nucleus
Chemical reactions involve changes in distribution of electrons forming compounds – no new elements
Radioisotopes are unstable radiosactive isotopes e.g. carbon-14
Half-life of a radioactive isotope is the time take for half of the atoms in a sample of the isotope to decay
Background radiation is the low level of ionising radiation surrounding us – mainly radon gas from rocks and soil
Uses for radioisotopes
1. Archaeology
- Used to determine age of objects comtaining carbon
- Measure of the changed ration between stable carbon-12 andn unstable carbon-14
2. Medicine
- Cobalt-60 gamma rays used in radiotherapy to treat cancer
3. Food Preservation
- Cobalt-60 preserves food by irradiation
See Scientists for information on Marie Curie and Henry Bequerel
