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Period: 200 to
Scientist's History
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450
Aristotle
Aristotle is a scientist from acient greece who believe that atoms were not made of different sizes and had regular shapes this made him believe that all substances are made of 4 of the following elements fire,wind,earth and water -
460
Democritus
Democritus was a scientist that lived in ancient greece that believe you could "cut" any substance until its no longer possible. Also that atoms are physically invisible meaning that between atoms lives empty space -
John Dalton
Is a scientist from England. He is the father of the atomic theory. He believe the atomic theory to be that elements are made up of tiny particles called atoms. Also that all atoms of a given element are identical , all atoms of different elements are different. Atoms of one element can combine with atoms of another element to give compounds. Finally atoms can combine in chemical reactions but they cannot be created or destroyed only changed. -
Marie & Pierre Curie
These scientist discovered that the radiation of Uranium compounds can be measured with precision under determined conditions, and that this radiation is an atomic property of the element of Uranium. They believed the Atom looked as though it was a planet with many electron rings around them. Evidence that the model was correct was the fact that the elements they discovered were accepted to be in the Periodic Table -
J.J Thomson
Thomson was a Englis scientist that discovered an electron in a number of different experiments from studying electric discharge. He claimed that the model of an atom was a circle of positive matter where electrons are placed by electrical force, he thought it looked like a cookie. With this he thought the electron was a component of all matter and figured the charge to mass ratio for the electron.
- Formula: e/m = -1.76 x 10 to the 8th power coulombs/g -
Henri Becquerel
A scientist that discovered radioactivity by accidentally putting crystal in the same drawer as a piece of photographic paper. He was going to do a different experiment, but it was canceled because of bad weather.When it started to clear up, he went to get his tools, Saw that the piece of material that contained Uranium, could produce an image on the photographic paper even in the absence of light. -
Robert Millikan
Millikan discovered the unit charge of the electron with his oil drop experiment this allowed the calculation of the mass of the electron and the positively charged atoms. Which formed the formula e = 1.60 x 10 to the -19th power coulombs. He also discovered that the weight of an electron is 1836 times smaller than that of a hydrogen atom. -
Ernest Rutherford
Rutherford is an English scientist that discovered the nuclear atom as the result of the gold-foil experiment that involved the firing of radioactive particles through minutely then metal foils and detecting them using screens coated with zinc sulfide. The model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space. -
Neils Bohr
Is a scientist that experimented with the H spectrum inventing the Planatary model believing he marked the point to a more modern atom -
James Chadwick
Chadwick is a scientist that discovered the neutrons or non-charged particles in the atom's nucleus he did this by performing tests on a new type of radiation that scientists mistook for gamma rays -
Quantum model
The quantum mechanical model is based on quantum theory, which says matter also has properties associated with waves. According to quantum theory, it’s impossible to know the exact position and momentum of an electron at the same time. Also believe that the atom uses complex shapes.
