Half-life of a radioactive element
The half-life of a radioactive element is defined as the average
time interval during which half of the initial number of nuclei of the
element disintegrate.
Decay constant or disintegration constant
The decay constant or disintegration constant of a radioactive element is defined as the ratio of the disintegration rate at an instant to the number of undecayed nuclei of the element present at that instant.
Nuclear fission
Nuclear fission is a nuclear reaction in which a heavy nucleus of
an atom splits into two or more fragments of comparable size either
Spontaneously or when bombarded by a neutron, with the release of
enormous amount of energy.
Nuclear fusion
Nuclear fusion is a type of nuclear reaction in which lighter atomic nuclei (of low atomic numbers) fuse to form a heavier nucleus (of
higher atomic number) with the release of enormous amount of energy
Some shortcuts
- 1 millicurie = 37 Rutherford
- The activity of a radioactive material will decrease as the number of undecayed nuclei decrease with time
- Half life and mean life of a material doesn't change with time or with pressure or temperature etc
- Geiger Muller counter is used for detecting alpha and beta particles
- No radioactive substance emits both alpha and beta particles simultaneously. Also gamma rays are emitted after the emission of alpha or beta particles
- Rch = Rydberg's energy = 2.17x10-¹⁸ J = 13.6eV
- Activity of a substance is inversely proportional to the half life of the substance
Definition and properties of radioactivity
- 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.
- 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 doesn't have any relationship with
- radioactivity.
