P1.1 - The Particle Model

Question 1

What did John Dalton propose? (1800)

Answer 1

That everything was made of tiny spheres, called atoms
That atoms could not be divided

Question 2

What did JJ Thomson propose? (1897)

Answer 2

Discovered electron and hypothesis of Plum Pudding Model

Question 3

Describe the plum pudding model

Answer 3

Atoms were electrons scattered throughout a soup of positively charged ions like how plums are scattered in pudding.
This way the negative electrons cancelled out the sphere of positive charge, having its charge as neutral overall

Question 4

What did Rutherford propose? (1911)

Answer 4

He (correctly) proposed of atoms being mostly empty space
Dense mass in centre (nucleus) with positive charge
Surrounded by negative electrons

Question 5

Describe the gold foil experiment and what it proved

Answer 5

There was a thin layer of gold foil
A beam of alpha particles (helium) was shot at it
- Most particles went straight through: suggested atoms are mostly empty space
- Some deflected slightly: suggested nucleus had a positive charge, repelling alpha particles
- Very few bounced back: suggested there was some dense central mass in the centre (nucleus)

Question 6

What did Bohr propose? (1913)

Answer 6

That electrons orbited the nucleus in fixed shells