Atomic Structure

1. Atomic Structure
Objectives:
4.1 To compare the discontinuous
hypothesis and the continuous
hypothesis regarding the structure of
matter.
4.3 Describe Dalton’s Atomic Model.

2. There were many scientist that
contribute to the development of the
first models of matter
1. Aristotle
2. Democritus
3. John Dalton
Hypothesis –
First Models Of Matter
4. J.J. Thompson
5. Rutherford
6. Bohr

3. Aristotle: Philosopher 300 BC (Greek)
HE PROPOSED THAT:
 All matter was continuous –no matter how
small a substance was, the original
properties were the same.
 Matter was made of the four basic elements
fire, water, air, earth.
 Matter could not be divided into smaller
particles (atoms)

4. Democritus: Philosopher 300 BC (Greek)
HE PROPOSED THAT:
 Matter was discontinuous
 Matter can be broken into smaller
particles
 Defined the term atom

5. First Models
• Despite Democritus’ accuracy,
Aristotle’s ideas were more widely
accepted.
• Neither man was a scientist and
neither did any experiments.
• They were both thinkers and
came up with ideas to explain
what they saw in the world
around them.

6.  He is known as the father of the Atomic
Theory.
 He formulated four main points concerning
atoms:
Developed by John Dalton
1) All matter is composed of tiny
indivisible particle called atoms.
2) All atoms of the same element are
identical (same).
3) Atoms of different elements are
different.
4) During a chemical reaction atoms
combine to form new products.
Memorize

7.  Even today, basic principles of
his theory are still true.
 His model was modified to
explain new observations of
later chemists
Dalton’s Atomic Model

8. WHO SAID THE FOLLOWING?
“All matter is made of
earth, fire, air or water”
“Atoms of different
elements are different
“Matter can be broken into
smaller particles”
“No matter how small a substance
was, the original properties are the
same”

9. Original Theories
• Discontinuous (Democritis) – spaces
between particles
• Continuous (Aristotle) – no spaces
between particles. Four elements –
fire, water, earth & air.
• Dalton’s Theory – memorize 4 main
points

10. Activities
 WORKSHEET # 4