Atomic Structure

Matter: anything that has a mass

BUT…. What is matter made up of?

Matter is made up of atoms. An atom is the smallest particle of matter. It cannot be divided chemically.

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. Thomson

5. Rutherford

6. Bohr

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.

Did not know about atoms.

Democritus: Philosopher 300 BC (Greek)

HE PROPOSED THAT:

Matter was discontinuous

Matter can be broken into smaller particles Defined the term atom

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.

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

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

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”

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

Activities

WORKSHEET # 4