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250
Democritus Model of the Atom
400 B.C.E. -
250
Democritus
400 B.C.E. He came up with a theory that matter could not be divided into smaller and smaller pieces forever, eventually the smallest possible piece would be obtained. this piece would be indivisible. this smallest piece would be called “Atomos” meaning not to be cut. -
300
Aristotle
355 B.C.E. Aristotle developed the theory that all matter consisted of four elements: Earth, Air, Water and Fire. There were also four qualities: dryness, hotness, coldness, and moistness. Fire was dry and hot, water was moist and cold. 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. -
Jan 1, 1100
Henry 1 becomces king of england
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Jan 1, 1348
Black Death Strikes Europe
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Industrial Revolution
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First steam powered car
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Independence of the United States of America
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Joseph Proust
Proust became known for helping prove the idea that every pure chemical compound consists of elements in a definite proportion -
John Dalton
He proposed an Atomic theory that said all matter was composed of small indivisible particles termed atoms, Atoms of a given element possess unique characteristics and weight, and three types of atoms exist: simple, compound, and complex. His work identified chemical elements as a specific type of atom, rejecting Newtons theory. -
Invension of the walking machine
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Henri Becquerel
He accidentally discovered radioactivity in uranium-containing pitchblende. He did this by noting the photographic plate upon which the pitchblende had been on was fogged. He also discovered uranium compounds fogged the plates. -
Thomson's Plum Pudding Atom Model
The Plum Pudding Model is an atom model proposed by JJ Thomson, the physicist who discovered the electron. You can imagine a plum pudding wherein the pudding itself is positively charged and the plums, dotting the dough, are the negatively charged electrons. -
J.J. Thomas
He experimented with a glowing glass tube and the hum of electricity. In his experiments he made a proposal, that these mysterious rays are streams of particles much smaller than atoms. He called these particles “Corpuscles”. He suggested that these may make up all matter in atoms. His bold suggestion turned out to be correct, the mysterious rays were made up of electrons, small, negatively charged particles that are important parts of atoms. -
Max Planck
Planck derived a relationship between the energy and the frequency of radiation, this was based on the idea that the energy emitted by a resonator could only take on discrete values or quanta. The energy for a resonator of frequency v is hv where h is a universal constant, now called Planck's constant. -
Albert Einstein
He published the equation E=mc2. He was the first person to show and prove that atoms existed using a microscope. He proposed that light can be absorbed or emitted only in discrete packets called quanta. -
Rutherford Model of the Atom
Created by Ernest Rutherford -
Ernest Rutherford
Rutherford from his experiments at McGill found that a narrow beam of alpha particles became fuzzy on passing through a thin sheet of mica and set an undergraduate to investigate whether any alpha particles were reflected from metals, finding some were scattered directly backwards. From this he deduced that almost all the mass of the atom is concentrated in a nucleus, a thousand times smaller than the atom itself -
Robert Millikan
Millikan’s earliest major success was the accurate determination of the charge of an electron using the “falling-drop method” -
Bohr Atom Model
The Bohr model depicts the atom as small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the solar system, but with attraction provided by electrostatic forces rather than gravity. -
Neils Bohr
Created an explanation of atomic structure that underlies regularities of the periodic table of elements. He proposed a model of the atom that assumed the electron exists at a precise distances from the nucleus, as long as an electron remains in one location no energy is given off. Electrons have circular orbits and the angular momenta associated with allowed electron motion are integral multiples of h. -
Quantum Mechanical Model
an atom with a tiny nucleus with probability waves instead of sharp orbits to describe the distribution of electrons, which have fuzzy positions but definite energy levels. -
Start of World War 1
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Werner Heisenberg
Heisenberg’s famous principle of uncertainty, which lays down that the determination of the position and momentum of a mobile particle necessarily contains errors the product of which cannot be less than the quantum constant h and that, although these errors are negligible on the human scale, they cannot be ignored in studies of the atom. -
Erwin Schrodinger
Found an electron around the atom. He derived a set of equations or wave functions for electrons.Electrons confined in their orbits would set up standing waves of where an electron would be. The orbitals are described as clouds, the densest clouds would be where you have the greatest probability of finding an electron. -
Louis de Broglie
In Broglie’s thesis, which gained him his doctor's degree, containing a series of important findings which serve as the basis for developing the general theory nowadays known by the name of wave mechanics, a theory which has transformed our knowledge of physical phenomena on the atomic scale. -
Invention of electric guitar
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James Chadwick
Sir James Chadwick was an English physicist who discovered a neutral atomic particle using alpha particles. He noticed that this neutral particle had a mass close to a protons and this was the discovery of the neutron. -
Beginning of World War 2
