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Scientists. The atom. Democritus . - 400 BC- Greek philosopher - No experimenting Matter made up of indivisible particles = “ atomos ”. Dalton. 1801: Thomas Jefferson President 1802: John Dalton experimented and concluded…. 1806: Fall of Roman Empire . Dalton.

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Scientists

Scientists

The atom


Democritus

Democritus

- 400 BC- Greek philosopher

- No experimenting

  • Matter made up of indivisible particles =

    “atomos”


Dalton

Dalton

1801: Thomas Jefferson President

1802: John Dalton experimented and concluded….

1806: Fall of Roman Empire


Scientists

Dalton

1. Matter made up small particles= atoms

  • Cant be created, destroyed, or made smaller

    2. Atoms of same element are identical

  • Different elements = different atoms

    3. Chem. Rxn atoms separate, join, or rearrange

    4. Atoms of different elements can combine in whole number ratios: compounds.


1850 s steam

1850’s- Steam

  • Steam powered engines of ships, trains, & factories

  • Key Question’s of 19th Century=

  • “How to build more effective steam engines” and

  • “ How to predict behavior of steam at high temps and pressures.”


1896 uranium

1896- Uranium

- Uranium was found to emit strange energy:

- Radioactivity: warm to the touch

- Can unlock secrets to the atom


1898 marie curie

1898- Marie Curie

Concluded Uranium atom gave off radiation

( but another chemist discovered first)

Found Radium – led to cancer fighting drugs

Won two Nobel Peace Prizes

Found Polonium

Kept radioactive materials in her pocket

Died of leukemia from radioactive materials


1904 j j thomson

1904-J.J. Thomson

  • Plum Pudding Model/ Chocolate Chip Cookie

  • Discovered electrons ( 1897)

  • Experiment with cathode ray tube

    • Particles move toward positive end

    • Particles must be negatively charged

    • Disproved that the atom was indivisible

      (could be broken into parts)


Thomson versus rutherford

Thomson versus Rutherford


Rutherford s goldfoil experiment

Rutherford’s Goldfoil Experiment

Result:

majority passed straight through

some bounced @ large angles & straight back


1911 rutherford

1911-Rutherford

  • Discovered:

    • atom was mostly empty space

    • Atom had a dense positively charged center

  • Disproved the Plum Pudding Model

    • (he was a grad student of Thomson)


1913 bohr

1913-Bohr

  • Planetary model of atom

  • Electrons move in

    an orbit

  • Each orbit had a

    definite energy


1914 1918 world war i

1914- 1918: World War I


1926 schrodinger

1926- Schrodinger

  • Extension of Bohr’s model

  • The electron “cloud” shows where the electron is most likely to be

    • You have a 90%

      chance of finding

      the electron

  • Electrons move like waves


Quantum mechanical model

Quantum Mechanical Model


History of atomic models

History of Atomic Models

Dalton 1802

Thompson 1904- “plum pudding”

Rutherford 1911

Bohr 1913

“planetary model”

Quantum mechanical model


1927 heisenberg

1927- Heisenberg

Uncertainty Principle

Can not know the speed and the location of the e- at the same time


1932 chadwick

1932-Chadwick

  • Prisoner of war in WW1

  • Worked for Rutherford

  • Discovered neutron

  • Issue: mass of helium was 4 but it only had 2 protons


Summary video

Summary Video


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