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Chapter 2 Atom,Molucules and ions

Chapter 2 Atom,Molucules and ions - CHEMISTRY The Central...

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CHEMISTRY The Central Science 9th Edition Chapter 2 Atoms, Molecules, and Ions
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The Atomic Theory of Matter The Atomic Theory of Matter Dalton’s law of multiple proportions: When two elements form different compounds, the mass ratio of the elements in one compound is related to the mass ratio in the other by a small whole number. Atomic theory: Each element is composed of tiny particles called atoms All atoms of a given element are identical. In chemical reactions, the atoms are not changed. Compounds are formed when atoms of more than one element combine.
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Atoms are the building blocks of matter. The ancient Greeks were the first to postulate that matter consists of indivisible constituents. Later scientists realized that the atom consisted of charged entities. The Discovery of Atomic The Discovery of Atomic Structure Structure
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The atom consists of positive, negative, and neutral entities (protons, electrons, and neutrons). Protons and neutrons are located in the nucleus of the atom, which is small. Most of the mass of the atom is due to the nucleus. There can be a variable number of neutrons for the same number of protons. Isotopes have the same number of protons but different numbers of neutrons. Electrons are located outside of the nucleus. Most of the volume of the atom is due to electrons. The Modern View of Atomic The Modern View of Atomic Structure Structure
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The Atom The Atom
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Class Practice Problem Class Practice Problem The diameter of a U.S. penny is 19mm. The diameter of a copper atom, by comparison, is only 2.6 angstroms (Å). How many copper atoms could be arranged side by side in a straight line across the diameter of a penny?
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The Atomic Mass Scale 1 H weighs 1.6735 x 10 -24 g and 16 O 2.6560 x 10 -23 g. We define: mass of 12 C = exactly 12 amu. Using atomic mass units: 1 amu = 1.66054 x 10 -24 g 1 g = 6.02214 x 10 23 amu Atomic Weights Atomic Weights
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Atomic number (Z) = number of protons in the nucleus. Mass number (A) = total number of nucleons in the nucleus (i.e., protons and neutrons). By convention, for element X, we write Z A X. Isotopes have the same Z but different A. We find Z on the periodic table. Atomic Number, Mass Number, Atomic Number, Mass Number, and Isotopes and Isotopes
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How many protons, neutrons, and electrons are in an atom of 197 Au? Hydrogen has three isotopes, with mass numbers 1, 2, and 3. Write the complete chemical symbol for each of them. Class Practice Problem Class Practice Problem
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Average Atomic Masses Relative atomic mass: average masses of isotopes: Naturally occurring C: 98.892 % 12 C + 1.108 % 13 C. Average mass of C: (0.98892)(12 amu) + (0.0108)(13.00335) = 12.011 amu. Atomic weight (AW) is also known as average atomic mass (atomic weight). Atomic weights are listed on the periodic table.
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