1. History of the Atom Model
Air, earth, fire & water
450 BC
Democritus (Greek)-
World was made of 2 things:
Empty space
Tiny particles call atoms
(Atomus= indivisible)
Aristotle (Greek) Matter is continuous and not made of smaller particles
PROBLEM: Neither had any evidence.

2. History of the Atom Model
1782
Antonine Lavoisier (French)-
Law of Conservation of Matter (mass)
Matter is neither created Nor destroyed,
it is only rearranged.
Mass of reactants = Mass of products

3. History of the Atom Model
1799
Joseph Proust (French)-
Law of Definite Proportions
Atoms must combine in whole number ratios.
H vs H0 ½

4. History of the Atom Model
1799
Joseph Proust (French)-
Law of Multiple Proportions
Atoms can combine in different
whole number ratios.
H vs H202

5. Modern Atomic Theory (MAT) Developing
1803
John Dalton (English)-
“Father of Modern Atomic Theory”
Started teaching at 12 years old.

6. Dalton’s Atomic Theory
All matter is made up of atoms. Atoms are the smallest fundamental units of matter.

7. Dalton’s Atomic Theory
TRUE
All matter is made up of atoms. Atoms are the smallest fundamental units of matter.

8. Dalton’s Atomic Theory
TRUE
All matter is made up of atoms. Atoms are the smallest fundamental units of matter.
All elements consist of atoms which are indivisible & indestructible.

9. Dalton’s Atomic Theory
TRUE
All matter is made up of atoms. Atoms are the smallest fundamental units of matter.
All elements consist of atoms which are indivisible & indestructible.
FALSE
Nuclear reactions

10. Dalton’s Atomic Theory
TRUE
All matter is made up of atoms. Atoms are the smallest fundamental units of matter.
All elements consist of atoms which are indivisible & indestructible.
All atoms of the same element are identical in size, shape & mass.
FALSE
Nuclear reactions

11. Dalton’s Atomic Theory
TRUE
All matter is made up of atoms. Atoms are the smallest fundamental units of matter.
All elements consist of atoms which are indivisible & indestructible.
All atoms of the same element are identical in size, shape & mass.
FALSE
Nuclear reactions
FALSE
Isotopes

12. Dalton’s Atomic Theory
TRUE
All matter is made up of atoms. Atoms are the smallest fundamental units of matter.
All elements consist of atoms which are indivisible & indestructible.
All atoms of the same element are identical in size, shape & mass.
Atoms of different elements are different in size, shape, & mass.
FALSE
Nuclear reactions
FALSE
Isotopes

13. Dalton’s Atomic Theory
TRUE
All matter is made up of atoms. Atoms are the smallest fundamental units of matter.
All elements consist of atoms which are indivisible & indestructible.
All atoms of the same element are identical in size, shape & mass.
Atoms of different elements are different in size, shape, & mass.
FALSE
Nuclear reactions
FALSE
Isotopes
TRUE

14. Dalton’s Atomic Theory
TRUE
All matter is made up of atoms. Atoms are the smallest fundamental units of matter.
All elements consist of atoms which are indivisible & indestructible.
All atoms of the same element are identical in size, shape & mass.
Atoms of different elements are different in size, shape, & mass.
In a chemical reaction, atoms are rearranged, never created nor destroyed & they combine in whole number ratios.
FALSE
FALSE
TRUE

15. Dalton’s Atomic Theory
TRUE
All matter is made up of atoms. Atoms are the smallest fundamental units of matter.
All elements consist of atoms which are indivisible & indestructible.
All atoms of the same element are identical in size, shape & mass.
Atoms of different elements are different in size, shape, & mass.
In a chemical reaction, atoms are rearranged, never created nor destroyed & they combine in whole number ratios.
FALSE
FALSE
TRUE
TRUE

16. Dalton’s Atomic Model

17. Modern Atomic Theory (MAT) Developing
1839
Michael Faraday (English)-
Atomic structure might be related to electricity…it might have a charge.
Ben Franklin (English)-
2 types of charges
Positive (later proton)
Negative (later electron)

18. Problem with Dalton’s Atom Model?
Lacks subatomic particles…

19. Modern Atomic Theory (MAT) Developing
1897
JJ Thomson (English)-
Cathode Ray Tube Experiment
link

20. Thomson’s Plum-Pudding Model
+ - +
Protons & Electrons
Lots of empty space

21. Problem with Plum-Pudding Model?
+ - +
- +
+ and - attract

22. Modern Atomic Theory (MAT) Developing
1909
Ernest Rutherford (English)
Gold Foil Experiment
link

23. Modern Atomic Theory (MAT) Developing
The Results & The Explanation
Most of positive charges passed through
because the atom is mostly empty space.
Some of the positive charges deflected
because the atom contains some positive
charge.
Some of positive charges deflected straight
back because there is a concentrated area
of positive charge (nucleus).

24. Rutherford’s Atomic Model_
+++
++++
Nucleus- Contains Protons
Electrons surround nucleus
Lots of empty space

25. Problem with Rutherford’s Model?
+++
++++ _ _
+++
++++
+ and - attract
Why? Why? Why?
Don't the electrons get
pulled to the center
where the protons are?

26. Modern Atomic Theory (MAT) Developing
1913
Niels Bohr (American)-
Solar System Model-
Electrons are like planets that orbit the nucleus
link

27. Problem with Solar System Model?
Scientists found this model failed for atoms other than Hydrogen because it couldn’t predict the energy levels of electrons in atoms with more than one electron.

28. Modern Atomic Theory (MAT) Developing
1924
Louis de Broglie (French physicist)-
Wave and particle Model-
1926
Werner Heisenberg (German physicist)-
Uncertainty Principle

29. Modern Atomic Theory (MAT) Developing
1926
Erwin Schrodinger-
(Austrian Physicist)
Charge Cloud Model-
Basic Parts of the Atom Nucleus Electron Cloud
link

30. ATOM COMPOSITION The atom is mostly empty space
protons and neutrons in the nucleus.
the number of electrons is equal to the number of protons.
electrons in space around the nucleus.
extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water.

31. Nucleus is Very Massive
Protons - Positive Charge
Neutrons - Neutral
Electrons - Negative