1911
  
Rutherford's Model
          
     

In 1911, one of Thomson's students, Ernest Rutherford, found evidence that was different from Thomson's model.

In an experiment, Rutherford's research team aimed a beam of positively charged particles at a thin sheet of gold foil. Since Thomson's model said that the whole atom was a positive ball, Rutherford expected the positive particles to go right through the foil, because there wouldn't be strong enough positive areas to repel the positive charges.

However, several particles were strongly repelled, leading Rutherford to believe that there must be a strong area of positive charge in the middle of the atom. This came to be known as the nucleus.

Rutherford also thought that most of the atom's mass came from this nucleus because scientists had figured out that electrons had very little mass.
   
Rutherford thought that the center of an atom must have a postive ball of charge, known as the nucleus.
 
                 
     
Rutherford's Atom
    
                 
   
Later, Rutherford named the positively charged particles in the nucleus of an atom protons.
  
                 
         
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Click here to see a 1:56 minute video clip about Rutherford's Model. 1
        
                             
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1. Discovering the Elements. United Learning (1996). Retrieved April 28, 2006, from unitedstreaming: http://www.unitedstreaming.com/