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Period: to
Atom Timeline
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John Dalton
John Dalton, an English school teacher, used the law of conservation of mass, law of definite proportions, and the law of multiple proportions to form an explaination that factored in the those laws and put them into five statements. -
Michael Faraday
Studied how electricity affects solutions and developed the laws of electrolysis. -
J. Plucker
Built one of the first gas discharge tubes or cathrode ray tubes. -
Joseph John Thomson
Joseph was able to measure the ratio of the charge of cathode-ray particles to thier mass. He discovered his ratio was always the same, and it did not matter the meta used to make the cathode or the nature of the gas inside the ray-tube. He stated that all cathode rays must be composed of identical negatively charged particles, which were named electrons. -
Max Planck
The German physicist was studying the emission of light by hot objects. He thought that hot objects do not emit electromagnetic energy continuously. Planck determined that the object emits energy in small, specific packets called quanta. -
Nagoaka
He created a "Saturnian" model of the atom that has flat rings of electrons revolving around a positively charged particle. -
Albert Einstein
Eloborated on Planck's thoery by introducing the radical idea that electromagnetic radiation has a dual wave-particle nature. -
Robert A. Millikan
The American physicist measured the charge of the electron. Scientists found this helpful and used this information and the charge-to-charge mass ratio of the electron to determine the mass of the electron is roughly one two-thousandth the mass of the hydrogen atom, which is the smallest atom. -
Ernest Rutherford
The New Zealander and his partners Hans Geiger and Ernest Marsden bombarded a thin piece of gold foil with fast-moving alpha particles, which are positively charged particles with roughly four times the mass of a hydrogen atom. When they checked for the possibilty of wide-angle deflections, they were shocked to find that roughly 1 in 8000 of the alpha particles had been deflected back. He concluded that the force must be becuase of densely packed bundle of matter called the nuclues. -
Neils Bohr
The Danish physicist proposed a hydrogen-atom model which linked the atom's electron to photon emission. In the model, the electron can can circle the nuclues only in allowed paths, or orbits. When an electron is in an orbit , that atom has a definite, fixed energy. -
Aston
Through the use of a mass spectograph Aston discovered the existance of isotopes. -
Louis de Broglie
The French scientist determined that in many ways the behavior of electrons in Bohr's quantized orbits was similiar to the known behavior of waves. -
Erwin Schrodinger
The Austrian physicist used the hypothesis of electrons have a dual wave-particle nature to develop an equation that treated electrons in atoms as waves. The quantum theory describes mathematically the wave properties of electrons and other very small particles. -
Werner Heisenberg
Heisenberg's idea involved the detection of electrons. Electrons interact with protons which is how they are detected. The Heisenberg uncertainy principle states that it is impossible to determine simultaneously both the position and velocity of an electron or any other particle. -
Crockcroft/ Walton
Created alpha particles by building a linear accelerator and bombarding lithium with protons. -
James Chadwick
He discovered a neutral atomic particle with a mass close to a proton using alpha particles. This discovered the neutron. -
Enrico Fermi
He conducted the first controlled chain reaction releasing energy from the atom's nucleus. -
Abegg
Discovered that inert gases have a steady electron configuration which lead to their chemical inactivity.
