-
400
Democritus
Democritus was an ancient Greek philosopher who was an influential pre-Socratic philosopher and pupil of Leucippus, who formulated what is thought to be the first atomic theory. He believed that atoms can not be destroyed and only exist in a void. He preformed an experiment proving that everything was made of small invisable particles. His model was a solid sphere representing an atom.
citation: "Development of the Atmoic Theory." Development of the Atmoic Theory. N.p., n.d. Web. 25 Oct. 2014. -
Issac Newton
Newton formulated a theory of light, the three laws of motion and suggested a mechanical universe with small, solid masses in motion.Newton suggested that atoms are held together with attractions, otherwise known as forces. He also stated that "matter is formed of solid, massy impenetrable particles”.
Citation:"Sir Isaac Newton." Newton Summary. N.p., n.d. Web. 12 Nov. 2014 -
John Dalton
He had the Biliard Ball model. He believed that atoms of an element are identical and that atoms of each element are different from one another. Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass. He had a chemical philosophy. -
Michael Faraday
Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, developed laws of electrolysis. Faraday himself was not a proponent of atomism.Faraday placed two opposite electrodes in a solution of water containing a dissolved compound. He observed that one of the elements of the dissolved compound accumulated on one electrode.
Citation: "Chemistry Explained." Michael Faraday. N.p., n.d. Web. 23 Oct. 2014. -
J. Plucker
He was a pioneer in the investigations of cathode rays that led eventually to the discovery of the electron. He built one of the first cathode rays. He also found that he could change the position of the patch of glass that glowed by bringing a magnet close to the tube. Plucker interpreted the effect of the magnetic field as evidence that whatever produced this glow is electrically charged.
citation:"Julius Plucker." Julius Plucker. N.p., n.d. Web. 30 Oct. 2014. -
Dmitri Mendeleev
Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law. -
James Clerk Maxwell
James Clerk Maxwell's principal contribution to the atomic concept had to do with his theory of electromagnetism. His mathematical laws of electrodynamics, formulated between 1864 and 1873, describe the phenomenon of electromagnetic radiation and build directly upon the earlier speculations of Michael Faraday.
citaition:"James Clerk Maxwell." James Clerk Maxwell. N.p., n.d. Web. 10 Nov. 2014. -
Sir William Crookes
Discovered 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. Goldstein
Used a CRT to study "canal rays" which had electrical and magnetic properties opposite of an electron. -
G.J Stoney
Proposed that electricity was made of discrete negative particles he called electrons. He made significant contributions to cosmic physics and to the theory of gases. -
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
While studying the effect of x-rays on photographic film, he discovered some chemicals spontaneously decompose and give off very pentrating rays. -
J.J Thomson
He found the electron While experementing with the cathode ray tube.He was one of the first to experement with the cathode ray tube. He created the plum pudding model.
citation: Mrs.Crews Notes. -
Rutherford
Studied radiations emitted from uranium and thorium and named them alpha and beta. -
Marie Sklodowska Curie
Studied uranium and thorium and called their spontaneous decay process "radioactivity". She and her husband Pierre also discovered the radioactive elements polonium and radium.
citation:"Marie Curie - Biographical." Marie Curie - Biographical. N.p., n.d. Web. 12 Nov. 2014. -
Soddy
Observed spontaneous disintegration of radioactive elements into variants he called "isotopes" or totally new elements, discovered "half-life", made initial calculations on energy released during decay.
citation:"John Dalton." John Dalton. N.p., n.d. Web. 12 Nov. 2014. -
Max Plank
used the idea of quanta (discrete units of energy) to explain hot glowing matter.He was able to deduce the relation between energy and frequency.He published a paper on it in 1900.
citaition: "Max Planck - Biographical." Max Planck - Biographical. N.p., n.d. Web. 12 Nov. 2014. -
Nagaoka
Postulated a "Saturnian" model of the atom with flat rings of electrons revolving around a positively charged particle.
citaition:"Nagaoka's Saturnian Model of the Atom." Nagaoka's Saturnian Model of the Atom. N.p., n.d. Web. 12 Nov. 2014. -
Abegg
Discovered that inert gases had a stable electron configuration which lead to their chemical inactivity. -
Ernest Rutherford
Using alpha particles as atomic bullets, probed the atoms in a piece of thin (0.00006 cm) gold foil . He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus.
citation:"Ernest Rutherford - Scientist Supreme." Ernest Rutherford - Scientist Supreme. N.p., n.d. Web. 10 Nov. 2014. -
H.G.J Mosely
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 reorganize the periodic table based upon atomic number instead of atomic mass.
citation: -
Aston
Discovered the existence of isotopes through the use of a mass spectrograph. -
Neils Bohr
Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of sucessive orbital shells of electrons. He was a student of Rutherford's.
Citaition: Mrs.Crews Notes -
De Broglie
Discovered that electrons had a dual nature-similar to both particles and waves. Particle/wave duality. He supported Einstein.
citation:"Louis Victor Pierre Raymond Duc De Broglie." Broglie Summary. N.p., n.d. Web. 12 Nov. 2014. -
Cockcroft/Walton
Built an early linear accelerator and bombarded lithium with protons to produce alpha particles. -
Heisenberg
Described atoms by means of formula connected to the frequencies of spectral lines. Proposed Principle of Indeterminancy - you can not know both the position and velocity of a particle.
citation:"Heisenberg / Uncertainty Principle - Werner Heisenberg and the Uncertainty Principle." Heisenberg / Uncertainty Principle - Werner Heisenberg and the Uncertainty Principle. N.p., n.d. Web. 12 Nov. 2014 -
Schrodinger
Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom.
citaition:"Erwin Rudolf Josef Alexander Schrödinger." Schrodinger Summary. N.p., n.d. Web. 12 Nov. 2014. -
Paul Dirac
Proposed anti-particles . Anderson discovered the anti-electron (positron) in 1932 and Segre/Chamberlain detected the anti-proton in 1955..
Citation:"Paul A.M. Dirac - Biographical." Paul A.M. Dirac - Biographical. N.p., n.d. Web. 12 Nov. 2014. -
James Chadwick
Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron.
citation: Mrs.Crews Notes -
Enrico Fermi
Conducted the first controlled chain reaction releasing energy from the atoms nucleus.
Citaition:"Enrico Fermi and the First Self-Sustaining Nuclear Chain Reaction." Enrico Fermi and the First Self-Sustaining Nuclear Chain Reaction. N.p., n.d. Web. 12 Nov. 2014.
