DEMOCRITUS (born in 470dc)

Proposed the existence of an atom

Word comes from the Greek word “atomis” which means not to cut

ARISTOTLE (born in 384dc)

Rejected the idea of the atom

Said matter could be cut continually

Greek filosofers 1803 1897 1909

Their observations get the tree laws.

Law of Conservation of Mass

Law of Definite Proportions

Law of Multiple Proportions

Dalton’s theory proposed that atoms:

Are building blocks of matter

Are indivisible Atoms of same elements

are identical Atoms of different

elements are different. They unite in small whole

number ratio to form compounds.

-Thomson continued to view atom as a solid mass.

Model of the atom:

Negatively charged electrons embedded in a ball of positive charge.

Rutherford’s theory proposed that atoms:

most of the atom is empty space

dense, positively charged core

called it the Planetary Model

negative electrons orbiting the positively charged nucleus

John Dalton J.J. Thomson

-He was credited with the discovery of electron: a blow to Dalton’s indivisible atom.

.

Lord Rutherford

Rutherford’s Gold-foil experiment.-aimed alpha particles at gold foil-most passed throughResults:A few particles were deflectedSome particles even bounced back

SCIENTIFIC EXPERIMENTS

ATOMIC MODELS

18th century

Aristotle believed that it would ever be a particle of matter that could be divided.

Democritus believed that substances can be cut in smaller and smaller pieces eventually we have the smallest possible peace that still behave like the original substance

Believe Atoms com back

Notice certain characteristic are shared by all chemical compounds.

Idea of the atom rejected for Aristotle. Most people sized with Aristotle and the believe of atom was lost.

Maria Faura

1st period

HISTORY OF ATOMIC THEORY AND MODELING TIMELINE