1. History of the ATOM
Once Upon a Time …

2. Democritus Democritus of Abdera Greek Philosopher 400BC
“Atomos” compose the world.
Tiny, indivisible particles that retain the chemical identity of an element
Model of the atom
                           

3. Dalton John Dalton English School Teacher (began teaching at 15!!!)
Atomic Theory of Matter (on Next Slide)
Model of atom

4. Dalton’s 5 Postulates - Atomic Theory of Matter
All matter is composed of extremely small particle called atoms.
All atoms of a given element are identical and are different from those of any other element.
Atoms cannot be created, divided into smaller particles, or destroyed.
Different atoms combine in simple whole number ratios to form compounds.
In a chemical reaction, atoms are separated, combined or rearranged.

5. Dalton’s Influences Meteorological Studies (Weather) Democritus
Kept daily recordings of weather for 57 years
Democritus
Robert BOYLE (Irish chemist )
Jacque CHARLES
Joseph GAY-LUSSAC

7. Law of Definite Proportions
states that a chemical compound always contains exactly the same proportion of elements by mass.
Example: Water’s mass ratio is always the same.
H2O is

8. Law of Multiple Proportions
The law states that when chemical elements combine, they do so in a ratio of small whole numbers. For example, carbon and oxygen react to form carbon monoxide (CO) or carbon dioxide (CO2), but not CO1.3.

9. Thompson J.J. Thompson (Joseph John) English Physicist 1856-1940
Electrons – negative sub-atomic particle
“plum-pudding” model
Cathode-ray Tube Experiment
Model
Thompson
+ -
Positive and Negatively charged particles Scattered around (must be electrically neutral)

10. Rutherford Ernest Rutherford New Zealand Scientist 1871- 1937
Discovered the Nucleus and determined that it has mass and a Positive charge
Gold-Foil Experiment
Model -

12. Chadwick James Chadwick English physicist 1891-1974
Neutron – the neutral sub-atomic particle
Model of Atom -

13. Bohr Neils Bohr Danish Physicist 1885 – 1962
Quantized the energy levels electrons could exist in an atom
Model of the atom -

14. Current Model of the Atom
Many people
Still on-going
Electron Cloud Model
Model of Atom -