developing the model if an atom Flashcards
when and what did john dalton and Democritus agree with
in 1804 john dalton agreed with Democritus the fact that matter was made up if tiny spheres called atoms
what did john dalton and Democritus say about atoms
that they cant be broken up but he reckoned each element was made of a different type of atom
what did J J Thomson discover
particles called electrons that could be removed from atoms
what did J J Thomson realise
Dalton’s theory wasn’t right
what did thomson suggest
atoms were spheres of positive charge with tiny negative electrons stuck in them like a fruit in a plum pudding (plum pudding model)
what was the experiment that scientists in rutherfords lab tried
they tried firing a beam of alpha particles at a thin gold foil, (this was the alpha scattering experiment)
from the plum pudding model they expected the particles to go through the sheet or be slightly deflected
what did the scientist in rutherfords lab realise
that particles did go straight through the sheet , some were deflected more than expected but a few were deflected back the way they came
this was something the plum pudding model couldn’t explain
what did the scientist realise about the few particles that were deflected back
most of the mass of the atom must be concentrated at the centre in a tiny nucleus
this means the nucleus has a positive Charged since the alpha particles repelled
What did they also realise When the alpha particles pass straight through
That most of an atom is just empty space
What did Niels Bohr say
The electrons orbiting the nucleus do so at certain distance is called energy levels
What did evidence from further experiments suggest about the change in the model of an atom
Is it that it has a nucleus made up of a group of particles called protons which all have the same positive charge that add up to the overall charge of the nucleus
What did James Chadwick prove
The existence of the neutron which explain the imbalance between atomic and mass numbers
what does the nucleus contain
Protons which are positively charged and have a +1 relative charge
Neutrons which are neutral with a relative charge of 0
Its radius is about 10,000 times smaller than the radius of an atom
what do electrons do and what is the charge
go around the outside of the nucleus really fast
-1 charge
what is the radius of an atom
1 x (10)-10m
