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460
Democritus
(460 -370 B.C.) Democritus was a Greek philospopher who believed matter was not infinitely divisible. Democritus believed matter was made of up tiny indivisible particiles called atoms. Democritus caused many other people to question what they had always known. -
Period: 460 to
Atomic Theory Timeline Project
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Antoine Lavoisier
(1743 - 1794) Lavoisier contributed to chemistry by making known the understanding of combustion and respiration as caused by chemical reactions with oxygen. He has had definite proof that water is made up of oxygen and hydrogen. He named many substances and was very important to the Chemical Revolution. -
John Dalton
(1776-1844) Dalton was well known for his first delivered paper over color blindness and is still called 'Daltonism.' He was very interested in meteorology and this brought him to his view on atomism. He calculated atomic weights and determined the atomic structure of each compound. He wrote of his theories in 'New System of Chemical Philosphy.' -
Law of Conservation of Mass
The law of conservation of mass simply states that mass is neither created nor destroyed during a chemical reaction. It is convrved.The equation is: MASS reactants = MASS products. -
Dalton's Atomic Theory
The basic ideas of Dalton's Atomic Theory include:
-All matter is composed of atoms
-Atoms cannot be made or destroyed
-All atoms of the same element are identical
-Different elements have different types of atoms
-Chemical reactions occure when atoms are rearranged
-Compounds are formed from atoms of the constituent elements -
Dmitri Mendeleev
(1834- 1907) Mendeleev is known for formulating the periodic table of the elements that happens to be very similar to the modern periodic table. He discovered how to arrange the elements while writing his textbook. -
Robert Millikan
(1868-1953) Millikan's earliest success was the determination of an electron's charge. By using the 'falling-drop method,' he proved this quanity was constant for all electrons. That demonstrated the atomic structure of electricity. -
Ernest Rutherford
(1871-1937) Rutherford did much research on the properties of the radium emanation and the alpha rays. His investigations led to the discovery of the atom in 1910. This was a major discovery in the scientific community. -
Niels Bohr
(1885-1962) Bohr's research was directed towards the atomic nuclei. He proposed a theory called the liquid droplet theory. This helped other chemists understand mechanism in the future. -
Erwin Schrodinger
(1887-1961) Schrodinger's great discovery was Schrodinger's wave equation. Also, Schrodinger was not satisfyed with Bohr's orbit theory and believed the atomic spectra should be determined by a type of eigenvalue problem. -
Henry Moseley
(1887-1915) Moseley did much work with x-rays. He studied them and saw it demonstrated the spectral line of platinum. He then experimented with the x-ray spectral lines of the elements from aliminum to gold. -
James Chadwick
(1891-1974) Chadwick proved that neutrons existed in 1932. Through this major discovery, Chadwick unknowingly prepared the way towards the invention of the atomic bomb. -
Cathode Ray Tube
A cathode ray tube is a special vacuum tube where an electron beam strikes a phosphorescent surfuce and produces images. Without the cathode ray tube, we would not have televisions, computer screens, phones, video game consoles, video cameras, or radar displays. Cathode ray tubes play a huge part in our day to day lives. -
Plum Pudding Atomic Model
JJ Thomson proposed the Plum Pudding Model. He propesed this model to help people visualize and learn about electrons. In a plum pudding, the pudding is positively charged while the plums, dotting the dough, are negatively charged electrons. Today this model is also referred to as the Chocolate Chip Cookie Model. -
Gold Foil Experiment
Ernest Rutherford preformed the gold foil experient in 1911. The results of this experiement concluded that an atom was not just empty space and electrons, and atom had a positively charged center that contained most of the mass. -
Rutherford Model
The Rutherford Model describes the atom having a central positive nucleus that is orbitted by negative electrons. It suggests that most of an atom's mass in located in the nucleus and that the rest was empty. -
Bohr Planetary Model
This model, is a planetary model in which negatively-charged electrons orbit a small positively-charged nucleus. This model shows that radiation is absorbed or emitte when an electron moves from one orbit to another. -
Quantum Mechanical Model
Erwin Schrodinger took the well known, Bohr Atom Model, a step further. He used equations to help find what position a certain electron is in. The Quantum Mechanical Model does not define an electron's exact path, but predicts the odds of an electron's location. -
Electron Cloud Model
The electron cloud model is a model representing that electrons are no longer just particles moving around the nucleus in a fixed orbit. Instead, with this model, we do not know exactly where they are and can only describe their location as an arbitary cloud around the nucleus. -
J.J. Thomson
(1956-1940) Thomson had an early interest in atomic structure. Thomson did an orginal study of cathode rays culminating in the discovery of the electron during 1897, This has affected our knowledge on the subject of cathode rays.
