Chapter 1.5 History Of The Atom

Question 1

Democritus
400BC

Answer 1

Thought of the concept of the atom

Question 2

J.J.Thomson
1897

Answer 2

Discovered Electrons
-found they were -vely charged
Created the Plum Pudding Model
A positively charged sphere with negatively charged electrons stuck throughout

Question 3

Niels Bohr
1913

Answer 3

Discovered that electrons orbited the nucleus in different energy levels/shells

Question 4

John Dalton
1808

Answer 4

Thought of atoms as tiny spheres
Atoms of each element are the same size and mass
Atoms of one element are different to another element
Can’t be divided or destroyed

Question 5

Ernest Rutherford
1911

Answer 5

Tested Plum pudding model (gold foil)
Fired alpha particles at gold foil
Thought the particles would go straight through as the atom was thought to be not very dense
Some bounced back at odd angles even some straight back
He said that the atom is mostly empty space with a dense nucleus in the centre made of positively charged protons

Question 6

James Chadwick
1932

Answer 6

Discovered the neutron
Found out the neutron had the same mass as the proton in the nucleus but had no charge

Question 7

Timeline (6)

Answer 7

1. Atom- Democritus
2. Tiny spheres - John Dalton
3. Electrons & Plum pudding model- J.J.Thomson
4. Nucleus - Ernest Rutherford
5. Neutron & Protons - James Chadwick