Atomic Theory

Question 1

John Joseph Thomson

Answer 1

-Atoms are not invisible
-Atom consists of a soft positively charged jelly-like sphere
-Negatively charged electrons were embedded (Like plums in pudding)
(Plum pudding model/ raisin bread model)

Question 2

Ernest Rutherford

Answer 2

-Atom consists of mainly empty space
-Most mass and all positive charge -> concentrated in centre (called the Nucleus)
-Negatively charged electrons would occupy space around nucleus
(Nuclear model)

Question 3

Niels Bohr

Answer 3

-An atom can have only certain, definite energies
-Corresponds to its electrons being in certain definite orbits
-Electrons can be compared to a solar system with its planets in definite orbits around the sun
(Planetary model)

Question 4

James Chadwick

Answer 4

• Identified a particle in nucleus with almost same mass of proton but no charge
• called a neutron

Question 5

John Dalton

Answer 5

-An element is composed of identical, invisible atoms characteristic of that element and no other
(Billiard ball model)