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Aristotle wasborn in 384 A.D,and died in 322 A.D. He believed that, in addition to the four basic elements, there were four basic properties; hot, cold, wet, dry. And that each basic element could contain two of the four properties. Elements, he thought, could change, if their properties were changed.
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He proposed a mechanical universe with small solid masses in motion.
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Dalton's atomic theory stated that all matter is composed of atoms, that all atoms of one element are identical, that the atoms can't be divided, created or destroyed, atoms of different elements can combine to form compounds, and that in chemical reactions atoms are combined separated or rearranged.His theory was changed over time, according to what was being discovered. Of his four statements two have been proved wrong, and two still form part of the modern atomic theory.
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While studying the effect of x-rays on photographic film, he discovered some chemicals spontaneously decompose and give off very pentrating rays.
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He used a CRT to experimentally determine the charge to mass ratio of an electron =1.759 x 10 8 coulombs/gram.
He also studied "canal rays" and found they were associated with the proton H + . Finaly he discovered the electrons leading him to his ''plum pudding" model. -
He observed spontaneous disintegration of radioactive elements into variants he called "isotopes" or totally new elements. Also he discovered "half-life",and made initial calculations on energy released during decay.
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Hantario sugestes that there is a central nucleus and that the electrons move in orbit like the rings around the planet Saturn.
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he published the famous equation E=mc 2
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His theroy was that the atom had a dense , positivly charged nucleus, and the elecrtons moved randomly in the space around the nucleus.
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He proposed that the moving particals like electrons have some properties of waves.
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Erwin Devoluped a mathmatical equation to describe the motion of electrons in atoms. This soon led to his electron cloud model. He also discovered the quantom theroy.
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Using alpha particles he discovered a neutral atomic particle with a mass close to a proton. This was led to discover the neutron.
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He belived that all matter was made from extremely small particals called atoms. The word came from the greek word "atomos" which ment "uncut" or "invinciable". Finally he thought that the solid particals were rough and prickley, while the liquid was soft and smooth.
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the days
