p17 - Defining the Atom All matter is composed of atoms...

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Defining the Atom All matter is composed of atoms Atoms are the smallest particle of an element that retains its identity in a chemical reaction. Atom comes from the Greek word atomos meaning indivisible. Powerpoint hosted on www.worldofteaching.com Please visit for 100’s more free powerpoints
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Democritus Democritus (460 BC – 370 BC) was among the 1 st to suggest the existence of atoms. Democritus believed that atoms were indivisible and indestructible. His approached was not based on scientific method and was not accepted until later scientific theory.
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Dalton’s Atomic Theory The modern atomic thought began with John Dalton (1766-1844) Dalton used experimental method to transform Democritus’s idea of atoms into a scientific theory. Dalton studied the ratios in which elements combine and the result was Dalton’s atomic theory.
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The ideas of Dalton’s Theory are: All elements are composed of tiny particles called atoms. Atoms of the same element are identical. Atoms of different elements are different. Atoms of different elements can physically mix together or chemically combine in simple whole number ratios to form compounds. Chemical reactions occur when atoms are separated,
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p17 - Defining the Atom All matter is composed of atoms...

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