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300
Aristotle
He believed that the earth consisted of four major elements; earth, fire, air, and water. Aristotle disagreed with Democritus and thought his ideas were worthless. Aristotle believed that reasoning was a better source of information than experimentation. -
400
Democritus
He was the first to theorize about the atom. He believed it was the smallest piece of matter. He used to word “atomos” which means indivisible. -
Alchemists
Alchemists were philosophers that created theories abou matter overtime. There is no specific experiment. Alchemists are also called hermits. -
Benjamin Franklin
He believed that there is an electric fluid present in all bodies and energy is gained or lost when objects are rubbed against each other. He stated that objects with opposite charges attract and same charges repel. -
Antoine Lavoisier
He established The Law of Conservation of Mass. This stated that energy cannot be created or destroyed. -
Jeremias Richter
He proved the law of definite proportions by weighing compounds and discovering that the ratio of elements were always the same. -
Joseph Proust
He analyzed sources of different compounds and found that the ratio was always the same of elements in a compound. This became the law of definite proportions. -
John Dalton
He established the modern atomic theory. -
MIchael Faraday
His discoveries led to the idea that atoms had an electrical component. He used electrodes and water in his experiment to discover that electrical forces joined atoms into compounds. -
William Whewell
He created the terms cation, anion, cathode, and anode by the negative and positive charges. -
Julius Plucker
He saw that when gas was put into a cathode ray one end of the gas lights up. By putting a magnet near the light, the light moved. -
Dmitri Mendeleev
He created the periodic table of elements by organizing the elements by atomic weights. -
William Crookes
He studied the effects of cathode rays. He aided in the discovery that atoms were made up of a lot of empty space. -
Wilhelm Roentgen
He used cathode rays to discover fluorescent rays, now called x-rays -
Henri Becquerel
He studied fluorescent properties of uranium salts. He contributed to the discovery of radioactivity. -
Marie and Peirre Curie
They worked with Bequerel to discover spontaneous radiation. They later won the nobel prize in physics in 1903. -
JJ Thomson
He discovered the electron by using cathode rays. He established the plum pudding model. -
Wilhelm Wein
He proved that canal rays deflected off of magnetic and electric fields proving cathodes are negative and anodes are positive. -
Max Planck
He believed atoms can emit quanta. His work was used by Einstein. -
H.G.J. Moseley
He proved van den Broek’s observation by studying the frequencies of x-rays in cathode rays. He discovered that the frequencies depended on the metal used in the anode which proved protons existed. -
Albert Einstein
He proved that light was quantized because light is made of photons. He proved that photons are proportional to frequency. -
Robert Millikan
He performed the oil drop experiment with Thomson. He measured the charge of an electron -
Ernest Rutherford
He performed the gold foil experiment. He established that the atom has a nucleus and the rest is empty space. He also predicted the existence o -
Niels Bohr
He updated Rutherford's version of the atom to show the directions of electrons. He also proved the orbits of electrons and how electrons could jump levels of orbit. -
Van den Broek
He suggested that it was a mistake to compare the atomic weight of an atom with the charge of the nucleus. He proved that the estimate of a charge on the nucleus is equal to the atomic number of the element. -
Louis-Victor de Broglie
He created an equation that showed that energy is proportional to mass and speed when moving through space. He also stated that wave length is inversely proportional to momentum. -
Werner Heisenburg
He established quantum mechanics. He was also the creator of the uncertaintly principle and calculated the behavior of electrons. -
Erwin Schrodinger
He calculated how to find the location of an electron using Bohrs model. His new model introduced the new concept of subenergy levels. -
CJ Davisson
He tested de Broglie’s prediction that electrons could have the properties of particles and waves. He confirmed this theory by defracting electrons in an experiment. -
James Chadwick
He discovered an unknown radiation with the approximate max of a proton. His discovery led to the addition of the neutron to the atomic model. -
Binning and H. Rohrer
They created scanning tunneling microscopy. This is used to see individual atoms within a metal. -
Eugen Goldstein
He proved that cathode rays glowed on the side of the cathode showing that the other side anode was positively charged. The protons and electrons move through tiny holes on the anode side that he called canal rays.
