1. Radioactivity
Chapter 8

2. Radioactivity
Radioactivity is the emission of alpha, beta or gamma radiation from the nucleus of unstable atoms.
It was discovered by Becquerel, who found that an uranium salt had affected a photographic plate. Pierre and Mari Curie found two new radioactive elements- polonium and radium. .
Becquerel,

3. Pierre and Marie Curie
For their work on radioactivity, the Curies were awarded the 1903 Nobel Prize in physics. A year later, Marie was awarded the Nobel Prize in chemistry for her discoveries of radium and polonium, thus becoming the first person to receive two Nobel Prizes.
Marie Curie ca Inset: Pierre Curie (Marie's favorite picture of her husband).

4. Geiger-Muller Tube
Radioactive radiation can be detected using a Geiger Muller tube

5. Alpha radiation
Alpha radiation consists of a stream of positively charged particles and so are deflected towards the negatively charged plate, and by a magnetic field.
Alpha particles consists of two protons and two neutrons which is the same as the nucleus of Helium.
The have low penetrating power and are stopped by a few centimeters of Air or a sheet of paper.
Examples of elements which emit alpha particles is americium-241(smoke detectors).

7. Beta Particles
Beta particles are simply electrons. A beta particle is formed when a neutron is changed into a proton and an electron.
They are more penetrating than Alpha particles and can penetrate up to 5mm of aluminium.

9. Gamma radiation
Gamma radiation is high energy electromagnetic radiation of very short wavelength. It is not deflected in electric or magnetic fields. Gamma rays have high penetrating ability.
Cobalt-60 gives off Gamma radiation. Used to kill cancerous cells.

11. Differences

13. Uses of Radio-isotopes
Medicine- Cobalt-60 kill cancer cells
Food preservation Gamma rays kill microbes
Industry- Tracers added to find source of leaking pipes
Archeology Carbon-14 dating by beta emmission

14. Radon