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John Dalton developes first universal atomic theory
Link text
http://www.answers.com/Q/Who_was_John_Dalton_and_what_did_he_do
But his theory had two flaws: First, atoms CAN be divided, and second, atoms of the same element aren't identical in mass. -
JJ Thomson discovered electrons
JJ Thomson was an English physicist credited with the discovery and identification of the electron; and with the discovery of the first subatomic particle. He discovered the electrons in 1897. Go to https://en.wikipedia.org/wiki/J._J._Thomson to see more. But, he assumed the positive charge of an atom was all one blob of matter with the electrons moving in orbits inside the nucleus. -
Marie Curie invented two new elements
Marie Curie invented two elements: radium and polonium. She also invented the term 'radioactive' to describe these two elements. Curie discovered radium by working to separate the substances in the ores and then used the electrometer to make radiation measurements to ‘trace’ the minute amount of unknown radioactive element among the fractions that resulted. -
Ernest Rutherford and alpha and beta particles
Ernest Rutherford differentiated and named alpha and beta radiation. By using an electrometer, he measured an electric current created by radiation instead of the technique of photographic plates. http://www.chemteam.info/Radioactivity/Disc-of-Alpha&Beta.html
But, a flaw was that a model of the atom with electrons moving around the nucleus would collapse. -
Ernest Rutherford proved that radioactivity involved the nuclear transmutation of one chemical element to another
Ernest Rutherford proved that radioactivity involved the nuclear transmutation of one chemical element to another. Rutherford's team, by using natural alpha particles, demonstrated 'induced nuclear transmutation', which is the conversion of one chemical element or isotope into another. http://www.mediander.com/connects/9603/ernest-rutherford/#!/p2/topic/27739443/ -
Ernest Rutherford discovered concept of radioactive half-life
Ernest Rutherford discovered the concept of radioactive half-life. He discovered the concept of radioactive half-life by the Geiger–Marsden experiment.The Geiger–Marsden experiment is and experiment which demonstrated the nuclear nature of atoms by deflecting alpha particles through a thin gold foil. https://en.wikipedia.org/wiki/Ernest_Rutherford -
Niels Bohr developed the Bohr model of the atom
Niels Bohr developed the Bohr Model of the atom, where energy levels of electrons are discreet and that electrons have a stable orbit around the nucleus but can jump from one energy level to another. But, one flaw is that charged electrons moving in an orbit around the nucleus should radiate energy due to the acceleration of the electron in its orbit. -
James Chadwick discovers the neutron
James Chadwick was assigned the task of tracking down evidence of Ernest Rutherford's "proton-electron pair" or neutron. In 1930 it was discovered that beryllium, when hit with alpha particles, sent out an energetic stream of radiation. But, later, it was generally recognized that it was difficult to reconcile the proton–electron model for nuclei with the Heisenberg uncertainty relation of quantum mechanics.
https://en.wikipedia.org/wiki/Discovery_of_the_neutron -
Enrico Fermi discovers beta decay
Enrico Fermi had developed a theory of beta decay to include the neutrino, presumed to be massless as well as chargeless. -
Lise Meitner discovered nuclear fission of uranium
Lise Meitner first discovered nuclear fission of uranium when it absorbed an extra neutron. This is the process is the basis of nuclear weapons that U.S. developed in World War II. But, the selection process may have been flawed. -
Murray Gell-Mann introduced concept of quarks
Murray Gell-Mann introduced the concept of “strangeness”, a quantum property and the force that holds the components of the atomic nucleus. He called these "quarks". But, the photon concept doesn't require classical. -
Amanda Pearson did this project
On November 1, 2017, Amanda Pearson started the atomic timeline project for physical science in eighth grade. On November 5, 2017, Pearson made the project public. (image below is not up to date)
