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Isaac Newton
Newton proposed a mechanical universe with a small masses in motion -
John Dalton
He proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass -
Michael Faraday
He studied the effect of electricity and developed the laws of electrolysis. -
J Plucker
He built the cathode ray tube. -
Lothar Meyer
He classified elements into 6 families by there valence. -
Dimitri Mendeleev
He arranged the elements into 7 groups. He discovered the periodic law, properties of elements "were periodic functions of their atomic weights." -
Sir Williams Crookes
He discovered that cathode rays had the following properties: travel in straight lines from the cathode, cause glass to fluoresce, impart a negative charge to objects they strike, are deflected by electric fields and magnets to suggest a negative charge, cause pinwheels in their path to spin indicating they have mass. -
E Goldsrtien
He used CRT to study canal rays -
GJ Stoney
He proposed electrons -
Wilhelm Roentgen
Using a CRT, he observed that nearby chemicals glowed. Further experiments found very penetrating rays coming from the CRT that were not deflected by a magnetic field. He named them x-rays -
Henri Becquerel
He discovered some chemicals spontaneously decompose and give off very penetrating rays when studying the effect of x-rays on photogenic film -
JJ Thompson
He used CRT to experimentally determine the charge to mass ratio of an electron= 1.759 x 10.8 coulombs/gram. He also studies canal rays and found they were associated with the proton H+ -
Rutherford
He studied radiation from uranium and named them alpha and beta. He estimated atom site and concluded mass was concentrated in the nucleus -
Marie Sklodowska
She studied uranium and thorium and called their decay process radioactivity. She and her husband Pierro also discovered the radioactive elements polonium and radium -
Max Planck
He used an idea of quanta to explain hot glowing matter -
Soddy
He observed spontaneous disintegration of radioactive elements into variants he called isotopes. He made initial calculations on energy released during decay. -
Nagoka
He postulated a saturnian model of an atom with white flat rings of electrons revolving around a positively charged particle -
Abegg
He discovered that inert gasses has a stable electron configuration which led to their chemical inactivity -
Albert Einstein
He discovered E=mc^2 -
Hans Geiger
He developed an electrical device. The tube clicked when it hit the alpha particles -
RA Milllikan
Oil drop experiment determined the charge e=1.602 x 10^-19 and the mass m =9.11 x 10^-28 gram of an electron -
Ernest Rutherford
Using alpha particles as atomic bullets, probed the atoms in a piece of thin gold foil. He established that the nucleus was very dense, very small and positively charged. He assumed that the electrons were located outside of the nucleus. -
HGJ Moseley
Using x ray tubes, determined the charges on the nuclei of most atoms. He wrote the atomic number of an element is equal to the number of protons in the nucleus. This work was used to recognize the periodic table based upon atomic number instead of atomic mass -
Aston
He discovered the existence of isotopes through he use of a mass spectrograph -
Niels Bohr
He developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of successive shells of electrons -
de Broglie
He discovered that electrons had a dual nature similar to both particles and waves -
Heisenberg
He described atoms by means of formula connected to the frequencies of spectral lines. He proposed a principle of indeterminacy which is you cannot know both the position and velocity of a particle -
Cockcroft/ Walton
They built an early linear accelerator and bombarded lithium with protons to produce alpha particles -
Schrodinger
He viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom -
Paul Dirac
He proposed anti-particles . Anderson discovered the anti-electron (positron) in 1932 and Segre/Chamberlain detected the anti-proton in 1955.. -
James Chandwick
Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron. -
Lise Meitner, Hahn, Stressman
Conducted experiments verifying that heavy elements capture neutrons and form unstable products which undergo fission. This process ejects more neutrons continuing the fission chain reaction. -
Enrico Fermi
Synthesized 6 transuranium elements and suggested a change in the layout of the periodic table. -
Glenn Seaborg
Conducted the first controlled chain reaction releasing energy from the atoms nucleus.
