Lesson 6. Flashcards
When did Dalton discover his model?
1803.
When did JJ Thomson discover his model?
1897.
How did JJ Thomson make his discovery?
Joseph John (J. J.) Thomson discovered the first subatomic particle, the electron, during his experiments. He found that beams of ‘cathode rays’ changed direction in electric and magnetic fields. He concluded that cathode rays were actually tiny particles that were negatively charged and much smaller than atoms.
What was Dalton’s Model?
Dalton did not know what atoms actually were, or even if they existed. He imagined them as tiny solid balls. He believed that all atoms of an element are identical and that different elements contain different types of atom.
What was Thomson’s model?
In his plum-pudding model, Thomson suggested that atoms are spheres of positive charge with electrons dotted around inside, like pieces of fruit in a cake. He believed atoms contained electrons and that atoms are neutral overall.
When did Rutherford make his discovery?
1909.
Who did Rutherford work with?
Hans Geiger and Ernest Marsden.
What was Rutherford’s experiment?
Him and his two colleagues pointed beams of positively charged particles, called alpha particles, at thin gold foil. The scientists expected the particles to go straight through the foil. Most did, but many of them changed direction slightly. Some even came straight back. It was as if the alpha particles had been pushed away by something.
Explain Rutherford’s model.
Rutherford explained the results by suggesting that an atom has a positively charged nucleus containing most of its mass. He also suggested that outside the nucleus, electrons orbit like planets in a solar system.
When did Bohr make his discovery?
1913.
Explain Bohr’s model.
Niels Bohr realised that orbiting electrons would be attracted to the oppositely charged nucleus and would rapidly spiral inwards. In 1913 he used mathematical models to improve Rutherford’s model. Bohr showed that electrons occupy fixed energy levels, or shells, around the nucleus.
