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430
The Greeks 430 B.C.E
The Greeks; Empedocles, Leucippus, Plato, Aristotle, and Democritus all began working with elements. They seperated the four parts, earth, air , fire and water. They later identified each element with a regular solid. -
John Dalton
John Dalton discovered the law of multiple proportions where whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the element are in the ration of small, whole numbers.In water the mass ratio of oxygen to hydrogen is 8:1 -
Joseph John Thompson
Thompson is famous for discovering the electron and he did through a series of experiments. He knew that is an electric current was passed through a vacuum tube, small glowing particles could be seen. He interpreted that the glowing stream bent toward a positively charged plate. Later experiments show that small particles of atoms called electrons now carried a negative charge. -
Hantaro Nagaoka
In 1904 Nagaoka developed an early but incorrect planetary model of the atom. He based his model of the atom around the rings of the planet Saturn. His model consists of a number of electrons of equal mass, arranged uniformly in a ring, and a positively charged sphere of large mass at the center of the ring. -
Max Planck
Max Planck is famous for discovering the equation E=hv where E represents the constant which he named after himself, Plancks constant. The value of this constant is 6.626x10^-34 J*sec. -
Robert A Millikan
Robrt A Millikan is most famous for his Oil Drop experiment in 1910. He discovered that the charge of an electron is about 1.5924(17)x10^-19 C. He also extended the Ultraviolet spectrum farther than the previous known limit. His last discovery was the law of motion of a particle falling toward the earth after entering earth's atmosphere. -
Ernest Rutherford
Rutherford is famous for his "Gold Foil Experiment" in which he tested J.J. Thompson's plum pudding Model. He shot energetic alpha particles at foil, and measured the angle of the particles as they came out the other end. He knew electrons where negatively charged so he approximated that atom consisted of positive charges therefore canceling eachother out. -
Niels Bohr
Niels Bohr created the Bohr Model which was derrived from Rutherfords model. Bohrs model shows that electrons travel in a sphere around the nucleus of an atom and have different levels of waves that are different distances from the nucleus. -
Erwin Schrodinger
In 1917 Schrodinger published his first ideas on the quantum mechanical model. He later studied the thesis of Louis de Broglie and quickly published his wave equation, or the quantum mechanical model which explains the properties of electrons. -
Werner Heisenberg
Heisenberg at 23 years of age published his theory of Quantum Mechanics, the mathematical desciption of the movement of subatomic particles. This theory won him the nobel prize in physics in 1932. -
Lous de Broglie
Developed the quantum theory and his experiments showed that waves (or radiation) caj behave like particles and particles can behave like waves. -
James Chadwick
Chadwick is famous for discovering the neutron in 1932 which earned him the Nobel Prize for physics in 1935 and led to the fissioning of Uranium-235 and, therefore, the atomic bomb.