The Atomic Model

Timeline created by 16beaty15942 in Science and Technology

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Event Date:	Event Title:	Event Description:
01/01/1417	Democritus	To Democritus, all matter consisted of tiny particles that could not be divided. Atoms in water were round and smooth. And atoms in solids were rough and prickly. He existed in 400 B.C. But his work was discovered in the Dark Ages in 1417.
02/02/1457	Aristotle	Aristotle thought that there was a limit to the number of times matter could be divided. By the 1800s, scientists had enough data from Aristotle's experiments to support an atomic model of matter.
09/06/1766	John Dalton	John Dalton studied the behavior of gases of air. He liked to predict the weather. Dalton had found evidence of atoms by measuring the masses of elements that combine when compounds form. Dalton said that no matter the sizes of the samples, the ratio of the masses of the elements in the compound is always the same. All compounds are similar. He proposed the theory that all matter is made up of individual particles called atoms, which cannot be divided.
12/18/1856	Joseph John Thomson	J. J. Thomson used the electric current. He hypothesized that the beam was a stream of charged particles that interacted with the air in the tube and caused the air to glow. Thomson figured out that the particles had a negative charge because they were attracted to a positive plate. J. J. discovered the first piece of evidence that atoms are made of even smaller particles. Thomson's model was neither negative nor positive, they were neutral.
04/23/1858	Max Planck	Max Planck's work was used by the famous Albert Einstein to study photons. Planck figured out the atoms can give off quanta, which is the minimum amount of any physical entity involved in an interaction.
08/15/1865	Hantaro Nagaoka	Nagaoka was a Japanese physicist, whom was mentioned in a paper Rutherford wrote in 1911 proposing the nucleus.
03/22/1868	Robert Millikan	Robert Millikan finished the atomic model with Thomson. He had measured the charge of an electron. Millikan was like Broglie, loved to deal with electrons. Robert had preformed the Oil Drop experiment. This was the downward gravitational force with the upward buoyant and electric forces.
08/30/1871	Ernest Rutherford	In 1899, Ernest discovered that uranium emits fast-moving particles that have a positive charge. When the Gold Foil experiment was preformed, it was concluded that more particles were deflected than exxpected. 1/20,000 was deflected by more than 90 degrees. The nucleus is a dense, positively charged mass located in the center lof the atom. All of an atoms positve charge is concintrated on its nucleus.
10/07/1885	Niels Bohr	Neils Bohr had worked with Rutherford, but focused more on the electrons. Bohr measrued the energy gained when electrons absorb energy and move to a higher energy level. He discovered that if the atom changes then the electron energy does too.
08/12/1887	Erwin Schrodinger	Schrodinger was an Austrian physicist and theoretical biologist. He is famous for his Schrodinger equation. Erwin was interested at an early age with experiments.
02/19/1889	Ernest Marsden	Ernest Marsden was one of Rutherford's students. When the Gold Foil experiment was preformed, it was concluded that more particles were deflected than exxpected. 1/20,000 was deflected by more than 90 degrees.
10/20/1891	James Chadwick	James Chadwick was mostly known for discovering the neutron. He figured out that neutrons do not have a charge. Chadwick was alive through World War 1, and he was in charge of the lab work.
08/15/1892	Louis de Broglie	Broglie was a French physicist and a Nobel laureate in 1929. Louis did a number of experiments to show his hypothesis was correct. His hypothesis was that electrons could act as both particles and waves.