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Aug 23, 1000
Aristotle
He did not think there was a limit to the number of times matter could be divided. He was a philosopher, so he came up with his own thoughts. -
Sep 5, 1000
Democritus
He believed that all matter consisted of extremely small particles that can't be divided. As a philosopher, he came up with his own thoughts. -
Robert Boyle
He proposed an early atomic theory of matter, formulated the first definition of an element. Robert conducted rigorous experiments with detailed documentation. Devised an air pump that helped him. -
John Dalton
Proposed the theory that all matter is made up of individual particles called atoms, which can't be divided. Developed a theory to explain why the elements in a compound always join in the same way. Measured the masses of elements that combine when compounds form. -
J.J. Thomson
Hypothesized that the beam was a stream of charged particles that interacted with the air in the tube and caused the air to glow.
He used an electric current to learn more about atoms. 1st evidence that atoms are made of even smaller particles. -
Ernest Rutherford
Discovered that uranium emits fast-moving particles that have a positive charge. Aimed a narrow beam of alpha particles at the gold. He observed the flash, and he could figure the path of an alpha particle after it passed through the gold. His student Ernest Marsden helped him. -
Niels Bohr
He agreed with Rutherford's model of a nucleus surrounded by a large volume of space. His model focused on the electrons. Worked with Rutherford and developed a model, the electrons move in spherical orbits at fixed distances from the nucleus. -
Werner Heisenburg
He developed the uncertainty principle, which restricts the accuracy with which some properties of atoms and particles can be determined simultaneously. He invented matrix mechanics to help him discover his theory. -
Hantaro Nagaoka
Hantaro Nagaoka suggests that an atom has a central nucleus. Experimented with different variety of atom models. -
Ernest Marsden
Ernest wanted to find out what happens to alpha particles when they pass through a thin sheet of gold. Marsden worked with Rutherford and beamed alpha through gold. He could figure out a path of an alpha particle after it passed through the gold. -
Louis de Brogile
Proposes that moving particles like elctrons have some particles of waves. Within a few years, evidence is collected to support his data. -
Erwin Schrodinger
He developed mathmatical equations to describe the motion of electrons in atoms. His work leads to the electron cloud model. -
James Chadwick
He confirms the existence of neutrons, which have no charge. He was studying Rutherford's model when he came across a theory of neutrons.
