Chemistry Notes - August 30, 2006 (2.1-2.3)

Chemistry Notes - August 30, 2006 (2.1-2.3) - August 30,...

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August 30, 2006 Chemistry Notes Section 2.1-2.3 Section 2.1 Democritus expressed the idea that matter consists of very small indivisible particles, which he named Atomos Not accepted by many, but somehow endured 1808 – John Dalton formulated a precise definition of the indivisible building blocks of matter that we call Atoms Hypotheses can be summarized: o Elements are composed of extremely small particles called atoms o All atoms of a given element are identical, having the same size, mass, and chemical properties. The atoms of one element are different from the atoms of all other elements o Compounds are composed of atoms of more than one element. The ratio of elements is either an integer or simple fraction o A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction. Joseph Proust – law of definite proportions – different samples of the same compound always contain its constituent elements in the same proportion by mass. The law of multiple proportions – if two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers. Different compounds made up of the same elements differ in the number of atoms of each kind that combine. Law of conservation of mass – matter can be neither created nor destroyed. Section 2.2 Atom – the basic unit of an element that can enter into a chemical combination. Atoms actually possess internal structure: they are made up of even smaller particles, which are called “subatomic” particles. Electrons, protons, neutrons
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This note was uploaded on 04/20/2008 for the course CHE 105 taught by Professor Woodrum during the Fall '06 term at Kentucky.

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Chemistry Notes - August 30, 2006 (2.1-2.3) - August 30,...

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