Chapter 19: Atoms and Radiation

Chapter 19: Atoms and Radiation

1. Particles

   • Gamma radiation is electromagnetic radiation from the nucleus
     • Gamma is the strongest, as it is the most penetrating, it can only be stopped by thick layers of concrete or many cm of lead
     • Used for treating cancer and to sterilize hospital equipment
     • Gamma isn't deflected by electric and magnetic fields
   • Beta is an electron from the nucleus
     • Beta is deflected by electric and magnetic fields
     • Atomic mass always stays the same
     • Atomic number increases by 1
     • Beta radiation can pass through air and paper but can be absorbed by a thin sheet of aluminum
     • Used In tracers for monitoring the thickness of different materials. This means that the thicker the material is the more radiation is absorbed and less reaches the detector
   • Alpha has 2 protons and 2 neutrons broken off the nucleus
     • Alpha can only penetrate through the air as it is absorbed by a few mm of paper.
     • Alpha is used in smoke detectors . It releases alpha particles which ionize the air, the smoke will absorb the alpha particles and then when it reaches the detector it will alter the ionization from the air which triggers the alarm
     • Deflected by both electric and magnetic fields. But alpha is always deflected less than beta and in the opposite direction
     • Atomic mass decreases by 4 and the atomic number decreases by 2

2. Background radiation

   • It is around us all the time. Comes from cosmic rays from space and man made sources such as fallout from nuclear weapons testing and nuclear accidents

3. Ionization

   • nuclear radiation changes atoms or molecules into charged particles

4. Some substances give out radiation from the nuclei of their atoms all the time, whatever is done to them. These are called radioactive substances

5. Half Life

   • The half life of a radioactive isotope is either the average time it takes for the number of nuclei of the isotope in a sample to halve, or the time it takes for the count rate from a sample containing the isotope to fall to its initial level