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Jun 14, 1000
Democritus.
*460 BC. what? ; His atomic theory states that everything is physically made op of atoms. He stated that atoms are indivisible and can never be broken down into pieces. how? ; This idea seems motivated by the question of how finely one can go on cutting up matter. -
Jun 15, 1000
Aristotle.
*384 BC. what? ; He believed in the four elements of air, earth, water and fire. Aristotle felt that regardless of the number of times you cut a form of matter in half, you would always have a smaller piece of that matter. -
John Dalton;
what? ; Dalton proposed the theory that all matter is made up of individual particles call atoms, which cannot be divided. how? ; Dalton made wooden spheres to represent the atoms of different elements. John Dalton pictures atoms as tiny, indestructible particles, with no internal structure. -
Wilhelm Roentgen
While using a CRT, he observed nearby chemicals that glowed. Some of the rays weren't deflected by the magnetic field. He these rays X-Rays. -
J. Plucker
He built the first Cathode Ray tube. These are used to make X-Rays. -
J.J Thomson;
what? ; Thomsons experiments provided the first evidenve that atoms are made of even smaller particles. how? ; Thomson figured out that atoms has neither positive nor negative chargers. J.J Thomson, a British scientist, discovers the electron, leading to his "plum-pudding" model. He pictures electrons embedded in a sphere of positive electric charge. -
Hantaro Nagaoka.
what? ; He proposed an alternative model in which a positively charged center is surrounded by a number of revolving electrons, in the manner of Saturn and its rings. how? ; The model was based around an analogy to the explanation of the stability of the Saturn rings (the rings are stable because the planet they orbit is very, very massive). The model made two predictions. -
Ernest Marsden.
what? ; Ernest Marsden worked with Ernest Rutherford and Hans Geiger to discover the deflection paths of alpha particles. Marsden was an undergraduate when he began working with Rutherford and Geiger to determine whether alpha particles can be scattered through a large angle. how? ; the team discovered that they could, and this became the basis for the discovery of the proton. -
Ernest Rutherford;
what? ; according to Rutherford's model, all of an atoms's positive charge is concentrated in its nucleous. how? ; -
Niels Bohr.
what? ; An electron in n atom can move from one energy level to another when the atom gains or loses energy. how? ; measure the energy gained when electrons absorb energy and move to a higher energy level. They can measure the energy released when the electron returns to a lower evenrgy level. In Niels Bohr's model, the electrons move in spherical orbits at fixed distances from the nucleous. -
Louis de Broglie.
what? ; introduced his theory of electron waves. how? ; This included the wave-particle duality theory of matter, based on the work of Max Planck and Albert Einstein on light. -
Erwin Schrodinger.
what? ; Schrödinger published in Annalen der Physik the paper "Quantisierung als Eigenwertproblem" on wave mechanics and what is now known as the Schrödinger equation. how? ; an electron cloud model, because based on the principles of quantum mechanics, one cannot exactly pinpoint the exact location..so he pictured the surrounding area around the nucleus as a "cloud". -
James Chadwick.
what? ; English physicist and Nobel laureate who is best known for discovering the neutron. how? ; He bombarded the alpha rays (coming out from a natural radioactive material) onBeryllium atom and observed that Beryllium artificially became radioactive for a short time it emitted material rays containing neutral particles having mass almost equal to proton.
