The history of the atom

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why do scientific ideas keep changing
new scientific evidence constantly leads to to scientific ideas to change, the model of the atom that we now accept has developed of time and may still change in the future
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first atom
originally when greek philosphers were the sicentists of the time atoms were thought to indivisible spheres and came from the greek word atomos - indivisible - aristotle did not agree with Democritus idea of the atom
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The plum Pudding model
because of the discovery of the electron instead of being an indivisible sphere the atom was thought to be a ball of positive charge with negetive electron embedded in it.
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Rutherford Geiger and Marsden
at a time when scientists were discovering all sorts of new things Geiger and Marsden, did an experiment called the scattering experiment. where they shot a beam of Alpha particles at a thin sheet of gold foil if the plum pudding model was correct
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ruther
plum pudding model was correct then the alpha particle would travel straight through - however as most of you know this was not the case - some of the particles traveled through as expected - but a few were deflected back and an even smaller bunch
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rutherford
were deflected all the way back - which meant that the plum pudding model was not correct and the positive charge was not spread out but cocentrated in a tiny area called 'the nucleus' - electrons were found on the outside
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Bohr and energy levels
it did not take long for new experiments to suggest another model - instead of tall the electrons rotating around the nucleus in the same area a scientist called bohr suggested that electrons rotated at specific distances at fixed energy level
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later
found that the positive charthe was divided into protons rather than being in a central space there was as may protons as there are electrons
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chadwick
in 1932 he discovered the neutron which he said had no charge but a mass
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Card 2

Front

first atom

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originally when greek philosphers were the sicentists of the time atoms were thought to indivisible spheres and came from the greek word atomos - indivisible - aristotle did not agree with Democritus idea of the atom

Card 3

Front

The plum Pudding model

Back

Preview of the front of card 3

Card 4

Front

Rutherford Geiger and Marsden

Back

Preview of the front of card 4

Card 5

Front

ruther

Back

Preview of the front of card 5
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