Development of the atom

Question 1

Atomic theory

Answer 1

• Everything is made out of tiny particles that can’t be broken down any further and are separated from eachother via empty space
• Proposed by Democritus in 500 BC

Question 2

John Dalton

Answer 2

• 1800s
• Things were amde out of small, solid spheres (atoms)
• Different types of spheres make up different elements

Question 3

Plum Pudding Model (PPM)

Answer 3

• JJ Thomson
• Series of experiments suggesting that atoms could not be solid spheres
• General ball of positive charge with negative electrons embedded in it

Question 4

Nuclear model

Answer 4

• Ernest Rutherford
• Fired positive particles at a sheet of gold. If PPM was right then the positive charge of the sheet would be too spread out and weak to effect the trajectory of the alpha particle
• Some alpha particles were deflected and some were deflected back
• Atoms had a compact nucleus of positive charge surrounded by a cloud of negative charge

Question 5

Niels Bohr

Answer 5

• Nothing to stop the nuclear model from collapsing
• Suggested that electrons orbitted the nucleus in shells

Question 6

Ernest Rutherford (after nuclear model)

Answer 6

• Suggested that the nucleus was made up of protons

Question 7

James Chadwick

Answer 7

• Suggested the nucleus also contained neutral particles called neutrons