Models Of The Atom Flashcards
What did Demokritos state about matter?(1)
Matter was made up of millions of tiny uncuttable pieces of that same matter
What did John Dalta state?(2)
Agreed with Democritus that matter es made up of tiny spheres that are uncuttable
Each element made up of a different type of atom
Who discovered the plum pudding model?(3)
J.J Thomson
What did J.J Thompson discover? Who did he prove wrong?
What was the plum pudding model?
Particles called electrons could be removed from atoms- Daltons theory wasn’t right (atoms could be brocken up)
A suggestion that the atom was a sphere of positive charge with negative electrons embedded inside
Why the plum pudding model made this way?
Available evidence at the time:
- solids cannot be squashed so atoms which make them up must be solid throughout
- rubbing two solids together often results in static charge so there must be something (electrons) on the outside which can be transferred as atoms collide
Who went on to test the plum pudding model?
Ernest Rutherford
What experiment did Rutherford conduct(4)?
Alpha scattering experiment
Describe Rutherfords alpha scattering experiment
An alpha source was used to fire a beam of alpha particles at thin gold foil.
Suspended in a vacuum with a scintillation screen curved around the gold foil at a distance
Why was gold foil used in Rutherford experiment?
Only metal that can be made very thin without cracking
What was observed from Rutherfords experiment and what conclusions could be made from these?
- most alpha did pass straight through the foil
> atom mostly empty space - small number of alpha particles where deflected at a large angle
> concentration of positive charge in the atom
 > like charges repel- positive alpha particles repelled by positive charge
- very small number of alpha particles deflected back
> positive charge + mass concentrated in a tiny volume in the atom (nucleus)
> nucleus must have a positive charge as it repelled positive alpha particles
Who refined Rutherfords model of the atom?
What did they add?
Niels Bohr
He took on board the positively charged nucleus and suggested the electrons orbit the nucleus certain distance called energy levels
What discovered the neutron?
James Chadwick
What did James Chadwick discover and what did this prove?
Since the proton has been discovered there was an imbalance atomic and mass numbers
By Chadwick discovering the neutron, this was explained
