History of the atom

Question 1

Dalton

Answer 1

Atoms were solid spheres.

Different spheres represent different atoms

Question 2

J.J. Thompson

Answer 2

Plum Pudding Model
Positively charged sphere with fixed negatively charged electrons
Concluded there was smaller negatively charged particles from measurements of mass and charge

Question 3

Rutherford

Answer 3

Gold Foil Shattering Experiment
Shot positive alpha particles at thin gold foil, expected particles to reflect slightly and most go through foil.
However, particles either went through the foil. were reflected at extreme angles or even repelled.
Plum Pudding model wrong.
Created Atomic Model- consisted of cloud of electrons surrounding nucleus

Question 4

Bohr

Answer 4

Thought Rutherford’s was incorrect as atom would collapse if electrons were in a cloud surrounding nucleus. Developed atomic model with electrons in shells orbiting nucleus, fixed shells with gaps between them

Question 5

Chadwick

Answer 5

With further experiments, nucleus divided into smaller parts- proton positive, 20 years later- Chadwick discovered neutrons.
Nuclear Model