1. And Now, Let’s Talk About Dead Guys
Famous Scientists who have made contributions to our understanding of Chemistry

2. Democritus ~400 BC Matter could be subdivided
Broken into little spheres he called “atomos”

3. Aristotle Taught Democritus Reject his theory and banished him
Matter is infinitely divisible
He alone set atomic theory back

4. John Dalton Englishman 1766 – 1844 Was colorblind
Based on his research, colorblindness was called “Daltonism” for a long time
Dalton’s Law (gases)
Atomic Theory

5. Dalton’s Atomic Theory (Atom is like a billiard ball)
All elements are composed of very small particles called atoms which are indivisible.*
All atoms of the same element are identical.*
Atoms of different elements are different.
Atoms of different elements combine in whole number ratios to form compounds

6. J.J. Thomson 1856 - 1940 Cathode Ray Tube Experiment
Discovered the electron
Won the Nobel Prize in Physics in 1906

7. J.J. Thomson Watch the stream of “light” respond to the magnet
Like charges repel
Opposite charges attract
Therefore, these rays were made of negatively charged particles

8. J.J. Thomson 1856 - 1940 Cathode Ray Tube Experiment
Discovered the electron
Like Charges Repel/Opposites attract
Electrons are negative

9. Ernest Rutherford 1871 – 1937 Worked in Thomson’s lab at Cambridge
Gold Foil Experiment
Won the Nobel Prize in Chemistry in 1908

10. Ernest Rutherford
Fired alpha particles at gold foil to see what happened
Deduced that most of the atom is empty space
Deduced that in the center is a densely clustered, positively charged nucleus

11. Niels Bohr 1885 – 1962 Won the Nobel Prize in Physics in 1922
Planetary Model of the Atom

12. Niels Bohr 1885 – 1962 Won the Nobel Prize in Physics in 1922
Planetary Model of the Atom

13. Robert Millikan 1868 – 1953 The Oil Drop Experiment
Determined the amount of electrical charge of 1 electron

14. Dimitri Mendeleev 1834 – 1907 Organized the first Periodic Table
Organized his table by atomic mass
Left spaces for elements he expected to fit
Predicted Eka- aluminum – gallium with a mass of around 68 and density of 6.0 g/cm3

15. Henry Moseley
1887 – 1915
Did work bombarding samples with X- rays to analyze the number of protons in an element
Now the chart is organized based on proton number not just on trends

16. Other Contributors
Antoinne Lavoisier- “Father of Chemistry” and the Law of Conservation of matter
James Chadwick – Discovered the neutron
Max Planck – The Quantum Mechanical Model of the atom.