1. Part 1 – The concept of the Atom
The History of the Atom
Part 1 – The concept of the Atom

2. A long time ago, in a galaxy country far, far away
There were two philosophers

3. One was Democritus Lived in Ancient Greece on the island of Sicily
First to use the term atom (atomos meaning indivisible)
Described the atom by mathematics of the day (His peer was Pythagoras)
Atom was described as the smallest part of a material
There were rock atoms, hair atoms, etc.

4. Democritus’s atom would have looked like this:
Solid and Indestructible
No electrons
No nucleus
No protons
No neutrons
No Experiments to support his ideas

5. The other was Aristotle
He lived in the heart of Greece (Athens)
Defined matter as composed of hot, cold, wet and dry
These properties related to fire, air, water, and earth
Everything differed by the percentages of each that composed the object

6. And the winner was: Aristotle And set chemistry back about 2000 years
Chemistry didn’t make a come back until the Renaissance

7. Antoine Lavoisier Frenchman in the late 1700s Was working with gases
He discovered that the amount of mass that one started with was equal to the amount of mass that one ended with – Law of conservation of mass.
Also discovered that oxygen caused things to burn
Some call him the Father of Chemistry

8. Joseph Proust Another Frenchman a few years after Lavoisier
Proposed Law of Definite Proportions
Roughly stated: a chemical could have only one ratio of atoms within it.
In other words, a compound will always have the same elements in the same ratio
Water has to be H2O and not HO or HO2

9. John Dalton
Took his own experiments and those of others to write a paper, which later became known as the Modern Atomic Theory
It gave a compilation of the information at the time and allowed other scientist to test his ideas.

10. Dalton's Atomic Theory
All matter is composed of extremely small particles called atoms, which cannot be subdivided, created, or destroyed.
Atoms of a given element are identical in their physical and chemical properties.
Atoms of different elements differ in their physical and chemical properties.
Atoms of different elements combine in simple, whole-number ratios to form compounds
In chemical reactions, atoms are combined, separated, or rearranged but are never created, destroyed, or changed.

11. An Analogy for Dalton’s atom
An atom is small, spherical and the same throughout.
A small atomic fireball

12. Dalton also gave us the Law of Multiple Proportions
Elements could combine in different ratios to produce different compounds
For Example, nitrogen and oxygen can form N2O, NO, NO2, N2O3, N2O4, and N2O5.

13. His ideas weren’t 100% correct, but they gave scientist a good start