Chapter 2.

Chapter 2. - Atoms Molecules and Ions Chapter 2 Chapter 2 1...

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Chapter 2 1 Atoms, Molecules, and Ions Chapter 2 Chapter 2
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Chapter 2 2 Atomic Theory of Matter The theory that atoms are the fundamental building blocks of matter reemerged in the early 19th century, championed by John Dalton.
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Chapter 2 3 Dalton’s Postulates All matter is composed of tiny particles called atoms .
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Chapter 2 4 Dalton’s Postulates All atoms of a given element have identical chemical properties. Atoms of different elements have distinct properties.
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Chapter 2 5 Dalton’s Postulates In chemical reactions, atoms of an element are not changed into different types of atoms; instead, a chemical reaction changes the way atoms are combined. Atoms are neither created nor destroyed.
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Chapter 2 6 Dalton’s Postulates Atoms form chemical compounds by combining in whole-number ratios. All samples of a pure compound have the same combination of atoms.
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Chapter 2 7 The Nuclear Atom
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Chapter 2 8 Subatomic Particles Protons and electrons are the only particles that have a charge. Protons and neutrons have essentially the same mass. The mass of an electron is so small we sometimes ignore it.
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Chapter 2 9 Isotope Designations Elements are symbolized by one or two letters. The atomic number is integer ABOVE Periodic Table symbol Uncharged atoms have equal protons and electrons Negative ions ( anions ) have EXTRA negative electrons Positive ions ( cations ) are MISSING some negative electrons
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Chapter 2 10 Isotope Designation This atom is MISSING 3 NEGATIVE electrons (a double negative is positive). An atom with 6 protons which is missing three electrons has 3 electrons left. Atomic number is number of protons, found ABOVE atom symbol. ALL carbon atoms have 6 protons. This isotope of carbon has a total of 12 protons and neutrons. Since it has 6 protons it must have 12 - 6 = 6 neutrons
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Chapter 2 11 Isotopes: Atoms of the same element with different masses. Isotopes have different numbers of neutrons. All atoms with the same symbol have same proton count 11 C 12 C 13 C 14 C
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Chapter 2 12 Fill In the Blanks Symbol 46 Protons 45 16 52 Neutrons 58 17 50 Electrons 43 18 52 36 Atomic No. 22 38 Mass No. 127 Hint: Do atomic number, protons, and symbol first!
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Chapter 2 13 Atomic Mass Atomic and molecular masses can be measured with great accuracy with a mass spectrometer. First one electron is stripped off of each molecule or atom of sample (left side) Next the positive ions (cations) are accelerated toward the magnet Magnet’s strength is adjusted so that only ions with a certain mass hit detector Heavier ions aren’t turned enough by the magnet; light ions turned too much
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Chapter 2 14 Average Mass Because in the real world we use large numbers of atoms and molecules, we use average masses in calculations.
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This note was uploaded on 05/12/2011 for the course CHEM 1201 taught by Professor Cook during the Spring '08 term at LSU.

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Chapter 2. - Atoms Molecules and Ions Chapter 2 Chapter 2 1...

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