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Period: 400 to
time span of time
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460
Democitus
Democritus, the laughing philosopher, was one of the founders of ancient atomic theory. He and the other atomists believed that there were tiny, indivisible bodies that make up everything. http://plato.stanford.edu/entries/democritus/ -
460
Indivisible solid sphere particle
The Indivisible Solid Sphere Model was developed by the famous Greek thinker Leucippus and his student Democritus. They were also the first ones to define atom. However, they considered it the smallest particle in nature and hence indivisible. -
John Dalton
John Dalton was the first to explain the behavior of atoms. His theory included these points:
1. elements are made of atoms
2. atoms of similar elements are identical
3. they cannot be subdivided, created, or destroyed
4. atoms of different elements combine in simple ratios to make chemical compounds.
5. In chemical reactions, atoms are combined, separated, or rearranged. http://en.wikipedia.org/wiki/John_Dalton -
Henry Becquerel
Henry Becquerel, while researching newly siscovered X-rays, was lead to studies of how Uranium salts were influenced by light. he discovered that the uranium salts spontaiously emitted penetrating radiation and, with further research, discovered radioactivity. http://www.nobelprize.org/nobel_prizes/physics/laureates/1903/becquerel-facts.html -
Joseph John (JJ) Thomson
JJ Thomson, a british physicist, discovered the electron and came up with the ‘plum pudding’ model of the atom. (18 December 1856 – 30 August 1940) -
Plum Pudding Model
the plum pudding model is a model of the atom developed by JJ Thomson, depicting the atom as a positively charged, dense 'pudding' with negatively charged electrons, or 'plums' scattered throughout. -
Marie Curie
Marie and her husband Pierre discovered the element Radium on December 26, 1898, and was the first woman to ever teach at the Sorbonne. http://www.nobelprize.org/nobel_prizes/themes/physics/curie/ -
Robert Millikan
Robert Millikan accurately determined the charge carried by an electron using the 'fall drop' method, and proved that this quantity was true for all electrons. http://www.nobelprize.org/nobel_prizes/physics/laureates/1923/millikan-bio.html -
Ernest Rutherford
Disproved JJ Thomson's theory of the atom's structure and, using the gold leaf experiment, discovers it to be more of a small, dense, positively charged nucleus surrounded by mostly empty space. http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1908/rutherford-bio.html -
Rutherford’s nuclear atom model
Rutherford's atom model is easily depicted as a small, dense, positively charged nucleus surrounded by mostly empty space and light, negatively charged electrons that orbit the nuclues. -
Niels Bohr
Niels Bohr proposed adding the new idea of quanta (put forth by Max Planck in 1901) to the atom model. In this new model, electrons existed in energy levels set at fixed distances from the nucleus. If the electron gained energy, it jumped an energy level further from the nucleus, and as it lost energy, it would jump a set closer to the nucleus. http://www.pbs.org/wgbh/aso/databank/entries/bpbohr.html -
Electron Cloud Model
The electron cloud model is an atom model where the electrons are not depicted as particles moving around the nucleus in a fixed orbit. Instead, we shouldn't know exactly where the location of the electron is, so it is depicted as just a vague area around the nucleus called the 'electron cloud'. http://www.pbs.org/wgbh/aso/databank/entries/bpbohr.html -
Erwin Schrodinger
assuming that electrons could be regarded as both particles and as waves, Schrodinger formulated a wave equation that accurately gave the energy levels of atoms. http://www.nobelprize.org/nobel_prizes/physics/laureates/1933/schrodinger-facts.html -
Erwin Schrodinger Wave equation
The equation that represents the electrons as a wave around the nucleus. -
James Chadwick
Chadwick helped Rutherford accomplish the transfusion of other light elements by bombardment with alpha particles, and in studying the properties and structure of atomic nuclei. http://www.nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.html -
Louis deBroglie
In 1924, deBroglie introduced the theory of electron waves and created a new branch of physcs; wave mechanics. http://answers.yahoo.com/question/index?qid=20081213190011AAPMaxQ -
Second Boer War begins
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Werner Heisenburg
Werner Heisenbug presented the idea that we cannot assign an election a position at any given time, or follow its orbit, and we cannot assume that the planetary orbits suggested by Niels Bohr actually exist. He says that mechanical quantities such as position, velocity, etc. should be represented by abstract mathematical structures called matrices. http://www.nobelprize.org/nobel_prizes/physics/laureates/1932/heisenberg-bio.html -
World War 1
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the Bohr model
Main Points of the Bohr Model
Electrons orbit the nucleus in orbits that have a set size and energy.
The energy of the orbit is related to its size. The lowest energy is found in the smallest orbit.
Radiation is absorbed or emitted when an electron moves from one orbit to another.
The Bohr Model has an atom consisting of a small, positively-charged nucleus orbited by negatively-charged electrons. Here's a closer look at the Bohr Model, which is sometimes called the Rutherford-Bohr Model. -
World War II Begins
Germany invades Poland. -
Albert Einstein
German theoretical physicist - left Germany in 1933 when Hitler came to power. Published many papers including one on the general theory of relativity. He was interested with problems of statistical mechanics and quantum theory, which led to his explanations of particle theory and the motion of molecules.
http://en.wikipedia.org/wiki/Albert_Einstein
