Chem Chapter 2

Chem Chapter 2 - Atoms, Molecules and Ions Chapter 2 Ch.2 1...

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Ch.2 1 Atoms, Molecules and Ions Chapter 2
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Ch.2 2 Democritus - 400 BC Abdera Sea of Marmara Caspian Sea Turkey Albania Romania Bulgaria Aegean Sea Athens Crete
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Ch.2 3 Democritus asserted that space , or the Void, had an equal right with reality, or Being, to be considered existent. He conceived of the Void as a vacuum , an infinite space in which moved an infinite number of atoms that made up Being (i.e., the physical world). These atoms are eternal and invisible ; absolutely small, so small that their size cannot be diminished (hence the name atomon, or " indivisible "); absolutely full and incompressible, as they are without pores and entirely fill the space they occupy; and homogeneous , differing only in shape, arrangement, position, and magnitude. Taken from Encyclopedia Britannica concise
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Ch.2 4 Dalton’s Atomic Theory (1808) 1) Elements are composed of extremely small particles called atoms How small? carbon density: 2.6 g/mL 6.022 x 10 23 atoms of C in 12g (Avogadro’s number) 12 g 1mL 12 mL ------------------------- ----------- = ------------------------ 6.022 x 10 23 atoms 2.6 g 15.6 x 10 23 atoms 7.7x10 -24 mL or cm 3 All atoms of a given element are identical . Atoms of different elements are different.
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Ch.2 5 Where do atoms come from? 15 billion years ago: Big Bang . Only hydrogen H (10 7 K) As it cooled, hydrogen clouds collapsed into stars. As stars became larger, atoms (as large as iron Fe ) were formed by fusion (10 9 K) Atoms larger than Fe were created in supernovae explosions (10 11 K) Evidence of the Big Bang : 1) expanding universe 2) background radiation (3K) 3) He detected 10 billion light years away
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Ch.2 6 1. Compounds are composed of atoms of more than one element . CO 2 2 atoms of O and 1 atom of C The relative number of atoms of each element in a compound is always the same. Carbon dioxide: 2 atoms of O ----------------- = 2 O per 1 C 1 atom of C 1. Law of definite proportions Different samples of the same compound contain the same proportion (by mass) of its constituents elements. 1. Law of multiple proportions If two elements combine to form more than one compound, the masses of one elements are in ratios of small whole numbers. Carbon monoxide: CO, 1 O per 1 C
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Ch.2 7 Calcium carbonate CaCO 3 2 1 3 C O =
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8 5) Chemical reactions only involve the rearrangement of atoms. Law of conservation of mass
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Chem Chapter 2 - Atoms, Molecules and Ions Chapter 2 Ch.2 1...

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