A brief presentation on the history of the atom

1800

Dalton: “Matter indeed, seems to consist of elementary lumpy

particles”

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1897

J.J. Thomson: Discovered the electron and proposed a model for the structure of

the atom: “Rasin in the pudding”

He knew that e- had negative charge

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1900

Max Planck: When you vibrate atoms strong enough, you can measure the energy only in discrete units (quanta).

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1905

Albert Einstein: Light absorption can release e- from atoms.“The Photoelectric effect”

(Nobel Prize 1921)

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1911

Ernest Rutherford: Bombarded atoms with α++. He came up with a new theory about the structure od

the atom: “Solar System” likeProblems: Loss of energy,

continuous spectrum expercted.

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1912

Niels Bohr: Introduced “Rules”1. Allowed Orbits2. Jump from Higher Energy orbit to Lower Energy orbit results to energy emission.

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1920

Bohr – Sommerfeld: Expanded the initial rules:

Orbits of different shapes (Quantum Numbers)

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1924

Wolfgang – Pauli: Electron spin, “Pauli’s exclusion principle”

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1926

Erwin Schrodinger: “Why not try to form a model for particle-

waves”

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1927

Werner Heisenberg: “Heisenberg’s uncertainty

principle”

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1932

James Chadwik: Discovery of the neutron

Carl Anderson: Discovered the positron, which Dirac had predicted in 1928 but was rejected at first

Heisenberg: Particles exchange photons

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1935

Hideki Yukawa: Exchange particles for strong force

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1940

Feynman, Schwinger: Four known forces, particles

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Source

• http://www.nobeliefs.com/atom.htm

Compiled by Jim Walker

• Presentation made by:

Tsourlidaki Eleftheria