AristotleAristotle- 400 B.C.
The Atom had been introduced by Democritus. Aristotle did not believe in the Atom Theory.
Aristotle believed that all matter was made of "The Four Elements" which are Fire, Earth, Air, and Water.
He did not have any proof to support his theory. The Atom Theory had no proof as well.
People believed and supported Aristotle's theory because in that time Aristotle was one of the greatest minds and had many followers.
DemocritusDemocritus: 460 B.C.
Democritus began with the idea that everything could be broken down into smaller peices. This is how he came upon his AtomTheory. Aristotle did not believe in this theory. Democritus stated that everything could be broken down into atoms. To Democritus the atom looked like a marble.
Antonie LavoisierAntonie Lavoisier found the two elements that make up water.
He named one Oxygen (Greek for becoming sharp) because of the acid in it.
He named the other Hydrogen (greek for water former).
His finding did not change the current atom model of his time, it just added another element.
John DaltonJohn Dalton developed the Atomic Theory in 1800. He still believed that the atom was the smallest unit of matter, and that it could not be bvroken down. He believed in Democritus' theory of the atom looking like a marble. John Dalton also tried to calculate the atomic weight of compounds. He also tried to come up with the atomic stuructures of atoms. http://en.wikipedia.org/wiki/John_Dalton#Atomic_theory
Henri BecquerelHenri Becquerel discovered uranium
produced x-ray radiation. Which led him to
discover radioactivity. All this happened as he was investigating phosphorescence.
Henri's discovery showed that the atom was not
undivisable or able to change shape. http://www.lycos.com/info/henri-becquerel--radioactivity.html
JJ ThompsonJJ Thompson discovered the electron using
the cathode-ray tube.
in 1904 Thompson thought the atoms was a sphere of positive
force with electrons around it. This is known as the
plum pudding model.
Thompson also created a mass spectrograph
which found isotopes. http://www.chemheritage.org/discover/chemistry-in-history/themes/atomic-and-nuclear-structure/thomson.aspx
Max PlanckMax Planck found the Quantum Theory.
The Quantum theory states "In 1900 Max Planck made a profound discovery in modern physics . He showed
that light must be emitted and absorbed in
discrete amounts if it was to correctly describe
observed phenomena Prior to then light had
been considered as a continuous electromagnetic
wave, thus the discrete nature of light was completely unexpected." http://www.spaceandmotion.com/quantum-theory-max-planck-quotes.htm
Marie and Pierre CurieMarie and Pierre Curie were a married couple. After
their marriage they continued to work together in science.
The couple discovered two elements:
the first is poloium
the sceond is radium
their discovery did dnot chage the model of teh atom it
just added to the known elements during that time.
Robert MillikanRobert Millikan was responsible for finding the charge
of a single electron.
He did this using his oil drop expirement. He
proved that subatomic particles do exsist.
Millikan is also credited with proving einstein. he did this by using the Photoelectric effect. http://en.wikipedia.org/wiki/Robert_Andrews_Millikan#Charge_of_the_electron
Ernest RutherfordErnest Rutherford discovered the nucleus.
His theory was the atom has a positive nucleus with negative electrons orbiting around it.
This changed the atom greatly because it was now known that most of the atoms weight is in the nucleus.
His model was known as planetary system model.
Ernest rutherford was the student of JJ Thompson. http://www.rsc.org/chemsoc/timeline/pages/1911.html
Niels BhorNiels Bhor proposed a new atom model that would allow the electrons to be outside the nucleus and in orbit around the nucleus.
Bhor said the electrons were on a special orbit.
His model is knowen as the Bhor Model. http://en.wikipedia.org/wiki/Bohr_model
Henry MoselyHenry Mosely found the relatinship between wavelengths,
x-rays produced, and the atomic number of a metal.
His finding became knowen as Mosely's Law. http://en.wikipedia.org/wiki/Henry_Moseley#Moseley.27s_research_breakthrough_in_physics_and_chemistry
Ewrin SchrodingerEwrin Schrodinger came up with the equation for quantum wave
His equation was the the second theory or explanation
for the reason electrons move when in an atom.
He tried to see electrons in packets that moved in waves. http://www.vigyanprasar.gov.in/scientists/eschrodinger.htm
Werner HeisenbergWerner Heisenberg came up with the uncertainty priciple. the uncertainty principle says that you cant measure the current position of a particle and also measure the position it will be in after it moves. http://en.wikipedia.org/wiki/Uncertainty_principle
James ChadwickJames Chadwick proved the exsistence of neutrons.
This affected the atom model greatly because another
subatomic particle was found in the atom.
James Chadwick changed the way the atom was viewed. http://www.nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.html