1. The history as we know it
MODELS OF MATTER
The history as we know it

2. Models of Matter 450 B.C. Empedocles (Greek)
Matter made up of only 4 elements
Earth, Air, Fire, Water

3. Models of Matter 400 B.C. Democritus First atomic theory
Not widely accepted – went against views of Socrates

4. Models of Matter
350 B.C.
Aristotle defends the 4 element model

5. Models of Matter
Four element model survives into the 1600’s despite numerous advances in scientific equipment and understanding

6. Models of Matter 1650 A.D. Robert Boyle
Definded ‘element’ as a pure substance that can’t be broken down
Believed air was a mixture, not an element

7. Models of Matter 1700’s A.D. Henry Cavendish
Discovers hydrogen gas by mixing acid and a metal
Later finds that water not an element (burning hydrogen in oxygen made water)

8. Models of Matter
1800’s A.D.
Generally accepted that matter was made of elements
…enter John Dalton…

9. Models of Matter 1808 A.D. John Dalton
Atom is a featureless sphere with no p+, e- or n (like a billiard ball)
Atoms are indivisible

10. Models of Matter 1897 A.D. J.J. Thomson
Sphere is positive with imbedded electrons (like a raisin bun)
Net charge of zero
No p+ or n

11. Models of Matter 1904 A.D. H. Nagaoka
Sphere is positive but electrons orbit in a ring (like planet Saturn)
Still no p+ or n

12. Models of Matter 1914 A.D. Ernest Rutherford
Small, positive nucleus surrounded by electrons (like bees around a beehive)
Still no neutrons
We’re getting closer!

13. Models of Matter 1921 A.D. Niels Bohr Built on Rutherford’s work
Special numbers of electrons in discrete energy levels
Similar to planets orbiting the Sun