Atomic Models Flashcards
Why were different models of the atom accepted in the past?
Because they fitted the evidence available at the time.
Why were new models of the atom developed?
Because scientists did more experiments, so new evidence was found and the old models were modified to fit it.
What models of the atom do we need to know?
- John Dalton’s
- J.J. Thompson’s
- Ernest Rutherford’s
- Niels Bohr’s
When did Dalton create his model of the atom?
At the start of the 19th century.
What was Dalton’s model of the atom?
He described atoms as solid spheres and said that different spheres made up the different elements.
What did Dalton’s model of the atom look like?
image
When did Thompson create his model of the atom?
In 1897.
What did Thompson conclude from his experiments?
That an atom must contain even smaller, negatively charged particles - electrons.
What was Thompson’s model of the atom?
It was known as the ‘plum pudding model’.
What did Thompson’s model of the atom look like?
image
When did Rutherford create his model of the atom?
in 1909.
Who helped Rutherford create his model of the atom?
His students:
•Hans Geiger.
•Ernest Marsden.
How did Rutherford create his model of the atom?
He conducted his famous gold foil experiment.
How did Rutherford’s gold foil experiment work?
He fired alpha particles (which are positively charged) at a very thin gold sheet.
What was Rutherford expecting the alpha particles to do in the experiment?
Because of the plum pudding model, he expected that most of the alpha particles would be deflected slightly by the positive ‘pudding’ that made up most of the atom.
What did the alpha particles actually do in Rutherford’s experiment?
Most of them passed straight through the gold atoms and a very small number were deflected backwards.
What did Rutherford conclude from his experiment?
That the plum pudding model couldn’t be correct.
What did Rutherford use the results from his experiment to do?
He came up with a model of the atom that could explain this new evidence.
What was Rutherford’s model of the atom called?
The nuclear model of the atom.
What was Rutherford’s nuclear model of the atom?
A tiny, positively charged nucleus at the centre, surrounded by a ‘cloud’ of negative electrons with most of the atom being empty space.
What did Rutherford’s model of the atom look like?
image
When did Bohr create his model of the atom?
in 1913.
What did scientists realise about Rutherford’s model?
That electrons in a ‘cloud’ around the nucleus of an atom would quickly spiral down into the nucleus, causing the atom to collapse.
What did Bohr do after scientists realised Rutherford’s electrons in a ‘cloud’ could not work?
He proposed a new model of the atom with four basic principles.
