Unit 1 - History Of The Atom

Question 1

When and What did John Dalton discover?

Answer 1

In the 19th century John Dalton describes the atom as a solid sphere and that different spheres make up different atoms

Question 2

When and What did JJ Thompson discover?

Answer 2

In 1897 JJ Thompson discovered electrons and that atoms weren’t solid spheres. He created the Plum Pudding model where a ball of positive charge had electrons stuck onto it

Question 3

Describe Ernest Rutherford’s experiment?

Answer 3

In 1909 he fired positively charged alpha particles at a thin sheet of gold. He expected most of the particles to pass straight through but more deflected than he expected.

Question 4

Why did Rutherford expect Alpha Particles to pass straight through?

Answer 4

Because they expected the positive charge of each atom to be spread out through the atom

Question 5

Describe the Model Rutherford created

Answer 5

Rutherford came up with the nuclear model, a positively charged nucleus where most of the mass is concentrated and a cloud of electrons surrounding the nucleus - hence most the atom being empty space.

Question 6

Why was it not possible for there to be electron clouds?

Answer 6

Because the protons and electrons would attract and the atom would collapse in on itself

Question 7

What did Bohr discover?

Answer 7

He realised electrons were contained in shells