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460
Democritus
First to propose the idea of the atom. 460 B.C. -
Isaac Newton
Theory that it is a mechanical universe with small objects constantly in motion. These small objects are atoms which Democritus proposed the idea of. -
John Dalton
Proposed "atomic theory". This theory states that everything is made up of particles called atoms. This theory is similiar to what Newton had said. -
Michael Faraday
Developed laws of electrolysis -
Julius Plucker
Built the first cathode-ray tube. This tube will be used to make many discoveries in the future. -
Dmitri Mendeleev
Creates the Periodic Table of Elements. At first, the table was sorted by the atomic mass of each element. Everntually, it will be changed to be sorted by atomic number by Henri Moseley -
James Clerk Maxwell
Proposed the theory of electromagnetism -
G.J. Stoney
Found negative particles in atoms which he called electrons. These electrons are located on orbital shells around the nucleus of the atom. -
Eugen Goldstein
Discovered Canal Rays which are rays which travel through holes or channels in cathode ray tubes. Goldstein noted that because these rays were traveling in the opposite direction, they must have an opposite charge. This discovery is made with the use of cathode ray tubes invented by Julius Plucker -
Wilhelm Roentgen
Created the x-ray. He also used the cathode ray tube invented by Julius Plucker to invent the x-ray. -
JJ Thomson
His experiments determined the charge mass ratio of an electron (1.759 x 108 coulombs/gram). -
Henri Becquerel
Discovered radiation by studying the effects of x-rays on photographic film. Alpha rays are fast moving helium atoms, beta rays are fast moving electrons, and gamma rays are photons, similiar to light, but much greater in energy. The invention of the x-ray by Wilhelm Roengten helped Becquerel in his discoveries. -
Marie and Pierre Currie
Invented the term "radioactivity" and discovered radium and polonium -
Frederick Soddy
Discovered isotopes -
Hantaro Nagaoka
Created the Saturnian Model of the atom which shows rings of electrons around the positively charged nucleus. This image shows the Saturnian model of Boron -
Richard Abegg
Discovered that Noble Gases have a astable electron configuration. This is because the amount of valence electrons satisfies the required amount of electrons needed in the last shell of an atom. (Octet Rule) -
Albert Einstein
Discovered the famous equation E=mc^2. This stand for Energy= Mass x the speed of light squared. -
Robert Millikan
Found the charge of an electron my means of the Oil Drop Experiment. -
Ernest Rutherford
Discovered the nucleus of an atom is small, dense, and positively charged. -
Henry Moseley
Created laws to arrange the periodic table of elements by the atomic number, or amount of protons present in the nucleus, instead of by the atomic mass of the element. -
Francis Aston
Uses the mass spectrograph to find isotopes and calculate the mass of isotopes. -
Niels Bohr
Explained atomic structures so that the periodic table of elements is sorted in successive order by the number of shells the atom has. This is an improvement upon the periodic table Dmitri Mendeleev created. -
John Cockcroft and Ernest Walton
Invented the linear accelerator and bombarded lithium with protoms creating alpha particles. This is also the first step in creating nuclear reactions. -
James Chadwick
Discovered the neutron with the use of alpha particles which were discovered by John Cockcroft and Ernest Walton.
