Radioactivity

1. Radioactivity

2. Discovered by Henri Becquerel in 1896 • He determined that the emission of radiation was spontaneous • Named the process radioactivity

3. Pierre and Marie Curie worked with a uranium salt named pitchblende • From this they managed to isolate polonium and radium • These elements accounted for the fact that the pitchblende was far more radioactive than the uranium content alone would indicate

4. Radioactivity is the spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation

5. Alpha radiation • An alpha particle is the same as a helium nucleus i.e. 2 protons and 2 neutrons • Alpha particles have low penetrating power but are highly ionising • Alpha particles are positive

6. Beta radiation • Beta particles are electrons. A beta particle is formed when a neutron is converted into a proton and an electron • Beta particles are of medium penetrating power and medium ionisation • Beta particles are negative

7. Gamma radiation • Gamma radiation is high energy electromagnetic radiation • An unstable nucleus emits gamma radiation to lose surplus energy • Gamma rays have very high penetrating ability

8. In a chemical reaction atoms and molecules are rearranged to give a new compound • In a nuclear reaction atoms change from one element to another

9. 238U92234Th90 + 4He2 • 14C6  14N7 + e- • Alpha decay: Mass number -4, atomic number -2 • Beta decay: Atomic number +1

10. Half-life • Half-life of an element is the time it takes for half of the nuclei in a sample to decay

11. Uses of radioisotopes • Medical • Archaeological • Agricultural • Food irradiation • Industrial