Timeline: Atomic Timeline

Dec 22, 1803

John Dalton

John Dalton noticed that compounds have something in common, compounds have a fixed composition. His theroy explains why elements in a compound always join the same way. His theory said that all matter is made up of individual particles called atoms. The atoms in the matter cannot be divided. PICTURE LINK: http://3.bp.blogspot.com/-8YCyKZI5eSE/Tssk5F9xuZI/AAAAAAAAAK8/A2S0RbS5WfM/s1600/Dalton.jpg
TITLE IMAGE LINK: http://upload.wikimedia.org/wikipedia/commons/f/fb/Schematicky_atom.png

Nov 18, 1897

Joseph John Thomson

In J.J Thomson's experiment he used a glass tube, and created an electrical current through the tube using metal disks and electricity. One side was negatively charged and one side was positively charged. A beam appeared through the center of the tube. When he placed charged plates on the side of the tube the beam was deflected from the path. This experiment showed that atoms are made of even smaller particles, the electron. PICTURE LINK: (Screenshot from book pg. 103)

Oct 26, 1911

Ernest Rutherford

Ernest Rutherford performed the Geiger-Marsden experiment. The experiment showed nuclear nature of atoms by sending particles through a thin sheet of gold. He asked his students to find alpha particles only with high deflection angles. This theory led him to create the Rutherford model of the atom in 1911. Rutherford discovered the nucleus of the atom. In Rutherfords experiment he did not focus on the electrons. PICTURE LINK: http://www.faqs.org/docs/qp/images/rfmodel.gif

Mar 19, 1913

Robert Millikan

Robert Millikan and one of his students performed the oil-drop experiment so that they could measure the charge of an electron. In this experiment they were able to measure the charge of a single electron. Scientises had earlier discovered the charge-to-mass ratio of the electron, but they were not able to meausre the charge of a single electron. PICTURE LINK: http://upload.wikimedia.org/wikipedia/commons/6/6f/Millikan’s_oil-drop_apparatus_1.jpg

Aug 21, 1913

Niels Bohr

In 1913 Niels Bohr created the Bohr model of the atom. Bohr said that the nucelus was at the center and then there were electrons that moved at a constant speed around the nucleus. One of the first problems was the lines did not fit Balmer's formula. PICTURE LINK: http://upload.wikimedia.org/wikipedia/commons/thumb/5/55/Bohr-atom-PAR.svg/2000px-Bohr-atom-PAR.svg.png

Apr 5, 1924

Wolfgang Pauli

Wolfgang Pauli discovered a new quantum degree of freedom. Wolfgang Pauli developed the Pauli exclusion principle. His principle said that no two electrons could exist in the same quantum state. PICTURE LINK: http://upload.wikimedia.org/wikipedia/commons/f/fb/Wolfgang_Pauli_ETH-Bib_Portr_01042.jpg

Oct 26, 1925

Electron Cloud Model

Ideas of the model were developed by Erwin Schrodinger and Werner Heisenberg. This model is different than Bohr's model, saying that we don't exactly know how the electrons move around the nucleus. PICTURE LINK: http://media.showmeapp.com/files/358317/pictures/thumbs/632840/last_thumb1358544050.jpg

Jul 12, 1939

Albert Einstein

Albert Einstein had many scientific theories. One idea that helped the United States during WWII was the atomic bomb theory. This started the Manhattan Project. They discovered that through fussion they could release a very large amount of energy with a small amount of matter (e=mc^2). PICTURE LINK: http://www.themattrix.com/wp-content/uploads/2014/04/atomicbomb.jpg

Oct 31, 2014