1. An alpha particle is nothing but a helium nucleus consisting of two protons and two neutrons with two unit of positive charge.
  2. \alpha particle coming out of a radioactive substances have very high velocity which might range from 1.4\times 10^7 to 1.7\times 10^7 m/s . Their path is a straight line and their motion can be observed in Wilson’s cloud chamber.
  3. \alpha particle is capable of producing intense ionization in the gas through which it passes. Its ionization power is 100 times greater than \beta particle and 10,000 times bigger than that of \gamma rays.
  4. It can affect photographic plate but its really week and feeble.
  5. \alpha particle can produce fluorescence effect when they fall on substance like zinc sulphide or barium platinocyanide.  This fluorescence can be observed through the microscope.
  6. \alpha particle is deflected by electric and magnetic fields and this shows that \alpha particle are charged particles.
  7. \alpha particles are scattered by heavy elements like gold.
  8. \alpha particle produces heating effect which is produced by stoppage of \alpha , \beta , \gamma rays by the radioactive substance.
  9. The E/M value of alpha particle was found by Rutherford to be half of that for hydrogen ion. The charge on each alpha particle was found to be twice that of a hydrogen ion. The mass of the \alpha particle was shown to be four times that of hydrogen. Therefore \alpha particle is the nucleus of hydrogen atom.