- Radioactivity was discovered by Henri Becquerel with photographic paper.
- Pierre and Marie Curie discovered polonium and radium.
alpha , beta , gamma .
- Groups of two protons and neutrons struck together .
- They have a positive charge (+).
- Have low penetrating power and are stopped by a sheet of paper.
- General equation:-2 from atomic number, -4 from mass number, move two places back in the periodic table and add the alpha particle .
- Formed when neutron in unstable nucleus is changed into proton.
- They have a negative charge (-).
- More penetrative and are stopped by 5mm of aluminium.
- General equation:
- Has no mass or charge.
- Only energy is emitted in waves of energy.
- It has high penetrating power.
- Can be stopped by thick lead.
Radioactive radiation is detected using Geiger-Müller tube.
Distinction between nuclear and chemical reactions
- New element may be formed.
- Change occur in nucleus.
- No chemical bonds are broken or formed.
- No new element formed.
- No change in nucleus.
- Chemical bond-breaking and forming occurs.
Uses of radioisotopes:
- Medical: Gamma radiation is used to kill cancer cells.
- Archaeological: Used for carbon-dating.
- Food irradiation: Gamma rays are used to kill disease-carrying organisms.
- Industrial uses: To detect leaks in pipeline radioisotopes are added and detected using Geiger-Müller counter.