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Jan 1, 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. -
Feb 2, 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. -
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. -
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. -
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. -
Hantaro Nagaoka
Nagaoka was a Japanese physicist, whom was mentioned in a paper Rutherford wrote in 1911 proposing the nucleus. -
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. -
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. -
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. -
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. -
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. -
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. -
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.
