Developing the Model of the Atom

Question 1

before the discovery of the atom what where atoms thought to be, when and who

Answer 1

1804, John Dalton - matter made up of tiny spheres that could not be divided

Question 2

what discovery led to the plum pudding model

Answer 2

the discovery of the electron

Question 3

what was the plum pudding model

Answer 3

suggested that the atom = a spheres of positive charge with tiny negative electrons within

Question 4

what experiment proved the plum pudding model wrong

Answer 4

Alpha scattering experiment
- Rutherford - fired beam of alpha particles at a thin gold foil
- according to plum pudding model, particles would have passed straight through , or only be slightly deflected
- BUT while most alpha particles passed through, some were deflected to the side and small number deflected back
- since deflected back, scientists realised most of the mass of the atom must be concentrated int he centre in a tiny nucleus —> nucleus must also have a positive charge
- nearly all passed through = most of atom was empty space

Question 5

how did Niels Bohr adapt the nuclear model

Answer 5

• suggested electrons orbit the nucleus at specific distances
• these theoretical calculations agreed with experimental observations

Question 6

what was later sicovered about protons

Answer 6

further experiments changed the model to have a nucleus made up of a group of particles (protons) which all had the same positive charge the added up to the overall charge of the nucleus