Solid spheres. Different spheres made up different elements.
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In what year did JJ Thompson disprove John Dalton?
1897
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Explain JJ Thompson's 'Plum Pudding Theory'...
His idea was that in an atom there were positively charge electrons and negatively charged 'pudding'. He knew this from his measurements of charge and mass.
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In what year did Ernest Rutherford conduct his experiment with gold foil?
1909
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Who were Rutherford's students?
Hans Geiger and Ernest Marsden.
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What was the gold foil experiment and what did they find?
In the experiment they shot positively charged particles at a thin sheet of gold. They expected (from the plum pudding model) most of them to bounce back. Although the majority passed through disproving Thompson's theory.
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What theory did Rutherford come up with?
He came up with the idea that there was a negatively charged nucleus, a cloud of positively charged electrons and a lot of space. This was called the theory of the nuclear atom.
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What did scientists realise about Rutherford's theory?
They realised that if he was correct the free-floating electrons would be attracted to the nucleus and the atom would collapse.
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How did Niels Bohr refine Rutherford's theory?
Bohr suggested that the electrons were in fixed shells/orbits and could exist anywhere in between. This was very close to the now accepted theory.
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How can scientist check their work?
Peer review and paper publishing.
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How does scientific knowledge evolve?
New evidence prompts new and improved ideas which can used to create predictions.
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Why were all these failed theories of the atom accepted?
They were accepted because at the time the evidence they had supported their theories.
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Other cards in this set
Card 2
Front
In what year did JJ Thompson disprove John Dalton?
Back
1897
Card 3
Front
Explain JJ Thompson's 'Plum Pudding Theory'...
Back
Card 4
Front
In what year did Ernest Rutherford conduct his experiment with gold foil?
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