The model of the atom Flashcards
In what year and who discovered that electrons could be removed form the atoms
1897, J.J. Thompson
What was the model called and what were the atoms like?
Plum pudding model. The atoms were spheres of positive charge with tiny negative electrons stuck in them like fruit of a plum pudding
What happened to the plum pudding theory
Didn’t last very long
What did Rutherford and Marsden tried firing in 1909
They tried firing a beam of alpha particles at thin gold foil.
What was expected for the plum pudding model
They expected the particles to pass straight through the gold sheet, or only be slightly deflected
What happened for the particles
Most of them went straight through the sheet, but some were deflected more than were expected but a few were deflected back
The plum pudding wouldn’t explain why
What did Rutherford realise
That most of the mass of the atom was concentrated at the centre of the tiny nucleus
What else did Rutherford realise about about the atom
It’s just empty space, and that the nucleus must have a positive energy charged. We know this as it repelled the positively alpha particles
What did then Rutherford lead this too
The creation of the nuclear model of the atom
Who tweaked Rutherfords idea
Bohr a few years later
What did Bohr do
He proposed a model where the electrons were fixed orbits at set distances from the nucleus.
What were these distances called
Energy levels
What did Bohr suggest
That electrons can only exist in these fixed orbits ( or shells ), and not anywhere in between.
What was the Model Bohr made called
Bohr model and is pretty close to our currently accepted model of the atom
