Exercises for p 17-19

  1. Complete the following using  Dalton, Thomson, Rutherford


  1. This simplest of the models has its limitations, but it can be used to explain physical changes Dalton
  2. Of the three models, this is the only one that does not include electrons.Dalton
  3. It is the first model that proposes electrons. Thomson
  4. He had a chance to prove his teacher wrong by firing alpha particles at a gold foil. Rutherford
  5. He was the first to propose that most of the atom’s mass was concentrated in the positively charged nucleus_Rutherford
  6. His model can be described as the “plum-pudding” or “chocolate chip” model because he evenly distributed the (+) and (-) charges Thomson
  7. This is the planetary model of the atom_Rutherford
  8. He imagined that atoms consisted of solid spheres, just like miniature bowling balls. Dalton
  9. He discovered “ cathode rays” or electrons which can be deflected by a strong magnet or by another electric field_Thomson
  10. In this model electrons are scattered outside the nucleus in what is mostly empty space_Rutherford
  1. The Rutherford Model In Detail



  1. Alpha particles are positively charged and unlike gamma radiation, they are an example of matter, not energy___TRUE
  2. Rutherford obtained similar results, regardless of whether he used thin gold, silver or platinum foil_____TRUE
  3. Most alpha particles bounced back after hitting the foil_____False
  4. The percent of particles which came back gives us a rough estimate of how big the nucleus is relative to the rest of the atom­_TRUE

4.         Complete the following table.














Does the model have positives and negatives?




Where is the mass of the atom concentrated?

evenly distributed throughout atom

evenly distributed throughout atom

concentrated in small nucleus

How did it improve the previous model?

electrons discovered

nucleus discovered

5.         a.         In what way is Rutherford's model of the atom similar to Thomson's?

Both have electric charges.

b.         Explain how they differ.

Thomson imagined an even distribution of electrons and positive charges. But Rutherford realized that the positives were concentrated in a small area of the nucleus. The mass of the atom also had to be bunched up in the nucleus. There was no nucleus or concentration of mass in the Thomson model.

6.         a.         In the gold foil experiment, what observation surprised Rutherford?

He was astonished to see alpha particles bounce back.

b.         What had he expected to happen when he fired alpha particles at gold foil? He expected all of the particles to go through the foil.