The Timeline of the Atom

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Democritus

400 BCE

Democitus was a Greek philosophers tha thought of the theory that there were things that were tiny and microscopic called atoms. His experience was if he could keep breaking down the same piece of gold an atom would be the only thing left.

work cites: . "Atomic Timeline." tripod.com. N.p.. Web. 27 Jan 2013. http://craigjm.tripod.com/physics.html.

picture cites: Democritus. N.d. n.p. Web. 27 Jan 2013. https://the-history-of-the-atom.wikispaces.com/Democritus.

John Dalton

1803

John found that everything is made of atoms and all atoms of a given element are identical in mass and properties. A chemical reaction is a rearrangement of atoms. He found this while doing something with gases.

Work cites: . "Atomic Timeline." tripod.com. N.p.. Web. 27 Jan 2013. http://craigjm.tripod.com/physics.html.

Picture cites: Dalton's atom. N.d. n.p. Web. 27 Jan 2013. <>.

Crookes

1879

Crookes studied the effects of sending an electric current through gas in a sealed tube. He noticed that as you removed gas from a tube, a glow would appear if you place a high voltage across it. He called them cathode rays.

Work cites: . "Atomic Timeline." tripod.com. N.p.. Web. 27 Jan 2013. http://craigjm.tripod.com/physics.html.

Picture cites: Crookes tube. N.d. n.p. Web. 27 Jan 2013. <>.

Becquerel

1896

He found that rays coming from a uranium ore affected a photographic plate like X-rays.His experiment led to the discovery of natural radioactivity.

Work cites:"Atomic Timeline." tripod.com. N.p.. Web. 27 Jan 2013. http://craigjm.tripod.com/physics.html.

Picture cites: Becquerel Atomic Theory . N.d. n.p. Web. 28 Jan 2013. <>.

Thomson

1897

He discovered the electron in a series of experiments designed to study the nature of electric discharge. Thomson discoverd electrons and made a sphere drawling of an atom around 1904.

Work cites:. "Atomic Timeline." tripod.com. N.p.. Web. 27 Jan 2013. http://craigjm.tripod.com/physics.html.

Picture cites: Thomson atom. N.d. n.p. Web. 27 Jan 2013. <>.

Rutherford

1911

Rutherford tested Thomson's hypothesis by devising his "gold foil" experiment. Rutherford reasoned that if Thomson's model was correct then the mass of the atom was spread out throughout the atom. He inferred a small, dense, positively-charged nucleus.

work cites:. "Atomic Timeline." tripod.com. N.p.. Web. 27 Jan 2013. http://craigjm.tripod.com/physics.html.

Picture cites: Rutherford's atom model. N.d. n.p. Web. 27 Jan 2013. <>.

Niels Bohr

1913

Bohr proposed the theory of the Hydrogen Atom. He thought of the idea of electrons moving in a circular motion around the nucleous.

work cites:. "Atomic Timeline." tripod.com. N.p.. Web. 27 Jan 2013. http://craigjm.tripod.com/physics.html.

Picture cites: Bohr's atomic model . N.d. n.p. Web. 27 Jan 2013. <>.

Chadwick

1931

In 1931 he discovered the neutron! He was looking at an alpha waves and neutrons started boncing off them.

work cites:. "Atomic Timeline." tripod.com. N.p.. Web. 27 Jan 2013. http://craigjm.tripod.com/physics.html.

Picture cites:Chadwick's atomic model. N.d. n.p. Web. 27 Jan 2013. <>.

Current Atomic Model

2013

Bohr and quantum mechanical model.

Picture cite: Current Atom Model . N.d. n.p. Web. 28 Jan 2013. <>.