Yr 9 Atomic Structure

Question 1

Democritus

Answer 1

-he discovered the atom at around 400 BC
-suggested that everything is made up of tiny, indivisible particles called atoms.

Question 2

John Dalton

Answer 2

-at around 1803
-proposed that all matter is made up of tiny, hard sphere particles called atoms
-all atoms in a substance are identical
(we now know these substances as elements)

Question 3

JJ. Thompson

Answer 3

-around 1897
-did experiments with cathode ray tubes
-showed that all atoms contain tiny particles called electrons
-realised atoms were divisible
-proposed the plum pudding model which had electrons embedded within a positively-charged ‘soup’

Question 4

Ernest Rutherford

Answer 4

-at 1909
-he did the gold foil experiment which disproved the plum pudding model
> a beam of +charged alpha particles passed through gold foil and most of them went straight through the foil, which was expected (as detected by the fluorescent screen)
>but others went in unexpected angles and some even shot back in the same direction which they came from
>these were the ones shot towards the center of the gold foil
-this means there was a small, dense centre of positive charge called the nucleus
-around the nucleus, was mainly empty space with some electrons orbiting around it

Question 5

Niels Bohr

Answer 5

-at around 1915
-proposed that electrons orbit around the nucleus with a set size and energy in shells

Question 6

James Chadwick

Answer 6

-at around 1932
-discovered atoms contain neutrons in the nucleus