The phenomenon of spontaneous emission of radiations by heavy elements is called radioactivity. The elements which shows this phenomenon are called radioactive elements.
- Radioactivity was discovered by Henery Becquerel in uranium salt in the year 1896.
- After the discovery of radioactivity in uranium, Piere Curie and Madame Curie discovered a new radioactive element called radium (which is 106 times more radioactive than uranium)
- Some examples of radio active substances are: uranium, radium, thorium, polonium, neptunium, etc.
- Radioactivity of a sample cannot be controlled by any physical (pressure, temperature, electric or magnetic field) or chemical changes.
- All the elements with atomic number (Z) > 82 are naturally radioactive.
- The conversion of lighter elements into radioactive elements by the bombardment of fast moving particles is called artificial or induced radioactivity.
- Radioactivity is a nuclear event and not atomic. Hence electronic configuration of atom donâ€™t have any relationship with radioactivity.