Models Of The Atom

Question 1

What did Demokritos state about matter?(1)

Answer 1

Matter was made up of millions of tiny uncuttable pieces of that same matter

Question 2

What did John Dalta state?(2)

Answer 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

Question 3

Who discovered the plum pudding model?(3)

Answer 3

J.J Thomson

Question 4

What did J.J Thompson discover? Who did he prove wrong?

What was the plum pudding model?

Answer 4

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

Question 5

Why the plum pudding model made this way?

Answer 5

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

Question 6

Who went on to test the plum pudding model?

Answer 6

Ernest Rutherford

Question 7

What experiment did Rutherford conduct(4)?

Answer 7

Alpha scattering experiment

Question 8

Describe Rutherfords alpha scattering experiment

Answer 8

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

Question 9

Why was gold foil used in Rutherford experiment?

Answer 9

Only metal that can be made very thin without cracking

Question 10

What was observed from Rutherfords experiment and what conclusions could be made from these?

Answer 10

• 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

Question 11

Who refined Rutherfords model of the atom?

What did they add?

Answer 11

Niels Bohr
He took on board the positively charged nucleus and suggested the electrons orbit the nucleus certain distance called energy levels

Question 12

What discovered the neutron?

Answer 12

James Chadwick

Question 13

What did James Chadwick discover and what did this prove?

Answer 13

Since the proton has been discovered there was an imbalance atomic and mass numbers
By Chadwick discovering the neutron, this was explained