half life

• the nuclei of radioactive atoms are unstable. They decay to form a completely different type of atom
• Radioactive decay is a random process. It is impossible predict when an individual nucleus will decay
• Half-life of the radioactive isotope is defined as the time taken for the number of radioactive buclei to reduce to one half of its initial value
• Different isotopes have different half-life values
• Some isotopes have a half-life value of thousands of years, while others have half-lives of a fraction of a second
• The half-life of a radioactive sample can also be defined as:

  • the time taken for the mass of the original radioactive element to reduce to one half of its initial value
  • the time taken for the activity to reduce to one half of its initial value
• Carbon-14 is unstable and radioactive. It has a half-life of about 5,700 years.
• Carbon-14 is used in a process called carbon dating. This method can be used to estimate the age of an object.
• Radioactive materials have many uses. One example of this is in medicine
• When selecting a suitable isotope for a specific application, it is important to consider:

  • the half-life of the isotope
  • the penetrating power and biological effects of the radiation