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427
Plato
He created the Theory of Forms which stated the material would is not real but only an image of the real world. -
440
Leucippus
Lucippus helped with the cration of the Atomic theory of Matter which stated when a substance is continually divided it will reach a piont that it can no longer be divided and become invisible -
460
Democritus
He worked with Leucippus to create the Atomic Theory that explained motion and change. He thought that atoms were indestructible and moved at random. He believed that the creation of substances was from atoms interlocking. -
Antonine Lavoisier
Known as the father of modern chemistry he recoginizes and names oxygen this year. He also recognizes its importance and role in combustion. -
Dmitri Mendeleev
He creates the first periodic table accoridng to atomic mass. He was able to use the table to predict the mass, density, melting point and other elements not yet discovered that were missing in the table. -
J.J Thomson
He suggested that there was sunatomic particle which was 1000th the size of an atom itself. These were later called electrons. His discovery was made while viewing cathode rays. These are beams of light created when electricity excites electrons in a vacuum tube. Thomson discovered that these rays were composed of previously unknown negitvely charged subatomic particles. -
Lord Ernest Rutherford
While working with uranium he discovered the existence of alpha and beta rays. -
Max Karl Ernst Ludwig Planck
He invented the Planck Constant. It is represented by h in the equation - frequency x h. The value of the constant is alwyas 6.63 x 10^34 j-s. He was always known as the founder of Quantum Mechanics. -
Antonious Van Den Broek
Broek proposes the idea that elements on the periodic table are more properly organized by positive nuclear charge rather than atomic weight. -
Robert Millikan
Discovered that the charge of an electron was negitive by preforming his famous oil drop experiement. He created am appartus that ionized the electrons so they would attach to an atom changing the charge to a negitive charge. -
Neils Bohr
he discovered that the electrons in an atom travel in robits around the nucleus. This discovery led to many new discoveries about atoms. -
Lord Ernest Rutherford
Successfully converts an element to another element, nitrogen to oxygen. Wasn't celebrated at fist because it was considered " alchemy." -
Erwin Schrodinger
He developed the quantum mechanical model which explains what orbital an electron is in. Quantum number are used to describe which orbital an electron may be in. The principle quantum number (n) describes the size of the orbital. The angular number (l) describes the shape of the orbital. They can be spherical, polar, or clover shaped. The magnetic number (m) describes the orbital direction the electron is spinning. -
Werner Heisenberg
He discovered the Umcertainty Principle. This states that the act of measuring one magnitude of a particle, be its mass, its velocity, or its postition, causes the other magnitudes to blur, Meaning it is impossible to measure the velocity and postition of an electron at the same time -
Louis de Broglie
Came up with Wave particle duality of Nature Theory. It proposed that light is both a wave and a particle. -
James Chadwick
Chadwick descovered the existent of nuetrons. Nuetrons help stabilize the protons and don't have an electrical charge. Nuetrons are the same size as protons. -
Glenn Seaborg
All of the elements in the modern periodic table have been discovered. The last few elements were found by Glenn Seaborg. -
John Dalton
In 1803 he announced the atomic theory. His theory states that 1) All matter is made of atoms. Atoms are invisible and indestructible. 2) All atoms of a given element are identical in mass and properties. 3) Compounds are formed by the combination of two or more different kinds of atoms. -
Empedocles
He was the first to discover the main elements - fire, water, air, and earth. he also believed that love and hate would make elements combined or seperate. He also came up with the Cosmogenetic Theory which was his attempt to expalin the seperation of elements. -
Aristotle
He began the early study of logic and also defined motion as the actuality of a potentiality. He also create the fifth idean aether, the make up of the heavenly spheres which adeed the four main elements of water, fire, air, and earth
