CHEM 1F92 Chapter Notes -Picometre, Cathode Ray, Alpha Particle
10 Sep 2014
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5th century bc, greek philosopher democritus said that matter is made up of small, particles called atomos (uncuttable) In 1808 english scientist and teacher, john dalton, formulated a precise definition of atoms. His work marked the beginning of the modern era of chemistry. The atomic theory is based on the following: 1. Elements are composed of extremely small particles called atoms: 2. All atoms of a given element are identical: 3. Compounds are composed of atoms of more than one element, with the correct ratio. Law of definite proportions: different samples of the same compound always contain its elements in the same proportion by mass. Law of multiple proportions: different compounds made up of the same elements differ in the number of atoms of each kind that combine?: 4. Atoms cannot be destroyed or created in chemical reactions, only separated, combine, or rearranged. Law of conservations of mass: mater can"t be created or destroyed.
