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Period: to
Atom Timeline
The history of the atom spaning from 375 BC (Democritus time) up to the 21st century. -
John Dalton
Source Dalton rationalized the first atomic theory where he stated that all matter is composed of atoms, that each element has unique atoms and that any change given to matter or an element is due to the rearranging of atoms whether they bond or seperate from each other. He left a basis to be improved upon. "Dalton Atomic Theory." Dalton Atomic Theory. N.p., n.d. Web. 05 Sept. 2013. -
Dalton's Model
Source Dalton's model was based on the ideas that atoms are the basic building blocks of all matter and that they are indestructible. He lacked the proper research to know the components of the atom, so they wer simply microscopic blocks with unique properties with fixed shapes and positions. "Dalton Atomic Theory." Dalton Atomic Theory. N.p., n.d. Web. 06 Sept. 2013. -
William Crookes
Source Crookes created his vaccum tubes that allowed him to use cathode rays, which would become later the firing of electrons. With cathode rays he found they created light and heat, providing basis for a 4th state of matter and spectrography. His research left a basis for future scientists such as J.J. Thomson. "William Crookes." Wikipedia. Wikimedia Foundation, 21 Aug. 2013. Web. 05 Sept. 2013 -
Joseph John Thomson
Source J.J. Thomson discovered the existence of electrons in 1897 while testing the charge of atoms, finding particles smaller than atoms. He created an atomic model with a positive nucleus that is surrounded by electrons in orbiting manner. "Joseph John Thomson." Homepage of the Chemical Heritage Foundation. The Berndt Group, n.d. Web. 05 Sept. 2013. -
Plum Pudding Model (JJ Thomson)
Source Presented by JJ Thomson years after finding the electron, he created the model where the atom has "plums" that are the electrons floating in the "pudding" that are the protons, which would cancel each other in the atom. The electrons were free of movement in rings but remained inside due to the positive cloud that attracted them. "Plum Pudding Model." Wikipedia. Wikimedia Foundation, 09 May 2013. Web. 06 Sept 2013. -
Rutherford Model
Source After his Gold Foil experiment where he discovered the nucleus, Rutherford created his atomic model 2 years later. His model consists of a nucleus that is composed of protons with electrons orbiting the nucleus. This model still is used today as a symbol for science. "Rutherford Atomic Model." Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. Web. 06 Sept. 2013. -
Ernest Rutherford
Source Rutherford found the existence of the Nucleus in an atom through the Gold Foil Experiment. He fired radioactive particles through a foil, where he noticed that some were deflected back, leading to his theory where atoms have most of their mass in the small nucleus made of protons and that most of the atom is empty space and surrounded by electrons. "Rutherford - Atomic Theory." Rutherford - Atomic Theory. RSC. Web, -
Bohr Model
Source Introduced by Bohr, his model represents a positive nucleus surrounded by negative orbits of electrons, where the size of the orbits relate to the energy they have. Improved upon Rutherford's model. Each orbit is fixed and radiation is emmited any time an electron moves orbits. Helmenstine, Anne M. "Bohr Model of the Atom." About.com Chemistry. About.com, n.d. Web. 05 Sept. 2013 -
Niels Bohr
Source His theory explains how atoms transmit light in fixed wavelenghts, finding that the electrons in an atom move around in orbits around the nucleus in defined quantities. As well that the number of electrons orbiting determine the properties of the elements. "Niels Bohr - Facts". Nobelprize.org. Nobel Media AB 2013. Web. 5 Sep 2013. -
Quantum Mechanical Model
Develped by Erwin Schrodinger, it was the model devised through the use of an his equation that would help to determine the number of electrons that are around the atom. It helped to see how the atom actually looks like and leaves room for improvement over the course of the years for other scientists. -
James Chadwick
Source James Chadwock in 1932 proved the existence of the neutron in the atom. While studying atomic desintegration, he noticed that the atomic mass was higher than atomic number, which led to his belief that there was a non charged particle in the nucleus. This led eventually to neutron bombarding due to its lack of charge, leading to nuclear bombs. "James Chadwick." James Chadwick. N.p., 21 Mar. 2010. Web. 05 Sept. 2013.
