According to Rutherford -
When a Gold Foil is subjected to alpha particles -
1) Most of the particles pass through
  (Because there is space between the electrons which are revolving         around the atom)
2) Some are deflected from their path -
   (Because they collide with electrons which have almost no mass)
3) A few bounce back due to their collision with the neucleas
    (Which is where there is all the mass)