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How the atom was discovered
Cards in this deck (7)
- 1what did john Dalton conclude -1800sHe did experiments, worked out some atomic weights and invented symbols for atoms and molecules. His most important conclusions are summarised below:
All matter is made of atoms
Atoms cannot be broken down into anything simpler
All the atoms of a particular element are identical to each other and different from the atoms of other elements
Atoms are rearranged in a chemical reaction
Compounds are formed when two or more different kinds of atoms join together - 2what did jj Thompson discoverJJ Thompson discovered the electron in 1897. This showed that the atom contained smaller pieces, whereas Dalton had thought that atoms could not be broken down into anything simpler.
- 3what did Rutherford discoverIn 1911 Ernest Rutherford used experimental evidence to show that an atom must contain a central nucleus. This was further evidence that an atom contained smaller pieces.
- 4what did Niels Bohr doNiels Bohr further developed Rutherford's nuclear atom model. He used experimental evidence to support the idea that electrons occupy particular orbits or shells around the nucleus of an atom.
- 5how was the early atom imagenedIn an early model, the atom was imagined as a sphere of positive charge with negatively charged electrons dotted around inside, rather like plums in a pudding. An experiment was carried out in 1905 to support this 'plum pudding' model of the atom but the results were unexpected.
- 6what experiment did Rutherford design to test the plum pudding modelRutherford designed an experiment to test the plum pudding model. It was carried out by his assistants Geiger and Marsden. A beam of alpha particles was aimed at very thin gold foil and their passage through the foil detected. The scientists expected the alpha particles to pass straight through the foil but something else also happened.Some of the alpha particles emerged from the foil at different angles and some even came straight back.
- 7what did they conclude from this experimentThe scientists realised that the positively charged alpha particles were being repelled and deflected by a tiny concentration of positive charge in the atom. As a result of this experiment, the plum pudding model was replaced by the nuclear model of the atom.
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- physics Flashcards on How the atom was discovered , created by ella stokes on 26/03/2017.
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