Atoms, Molecules, and Ions

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Chapter 2

• Atoms, Molecules, and Ions

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Dalton - 1803

• Each element is composed of extremely small
  particles called atoms
• All atoms of an element are identical all atoms
  of different elements are different
• Atoms are only rearranged in chemical reactions
  and are not created or destroyed
• Compounds are formed when atoms of elements
  combine and they do this with the same relative
  number and kind of atom

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Laws from Dalton

• Law of Constant Composition (CO2)
• Law of Conservation of Mass
• Law of Multiple Proportions (CO and CO2)

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Subatomic Particles - Electron

• J.J. Thompson
• Cathode ray tube
• Negative charge
• Charge to mass ratio
• http//www.sciencemuseum.org.uk/on-line/electron/r
  esources/electron.mov
• http//highered.mcgraw-hill.com/sites/0072512644/s
  tudent_view0/chapter2/animations_center.html

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Millikan Oil Drop Experiment

• Determined charge on the electron, so from c/m
  ratio he deduced the mass of the electron also.
• Diagram by Theresa Knott

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Experiment

• http//highered.mcgraw-hill.com/sites/0072512644/s
  tudent_view0/chapter2/animations_center.html

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The Rest

• Proton also found in cathode ray tube
• Neutron found much later (1932) by Chadwick

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Radioactivity - the Magic Bullet

• Becquerel, Marie and Pierre Curie study and
  describe radioactivity
• http//www.history.com/media.do?actionclipidtdi
  h_0420

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Three Kinds of Radiation

• http//highered.mcgraw-hill.com/sites/0072512644/s
  tudent_view0/chapter2/animations_center.html

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The Nuclear Atom

• Plum Pudding Model to be confirmed by Ernst
  Rutherford
• Famous Gold Foil Experiment conducted
• Planetary Model proposed
• http//highered.mcgraw-hill.com/sites/0072512644/s
  tudent_view0/chapter2/animations_center.html

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Modern View

• Electron charge -1.6 X 10-19 C e
• Abbreviated (-1)
• Proton same amount of charge but opposite in
  sign (1)
• Atoms are normally electrically neutral
• Masses expressed in amu (atomic mass unit)
  1.66054 X 10-24 grams
• Mass of proton mass of neutron 1 amu
• Mass of electron 5.486 X 10-4 amu

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continued

• Size ranges from 100 to 500 pm or 1 to 5
  angstroms (10-10m)
• Most of atom is empty space
• Marble on 50-yard line example
• This makes the nucleus very dense matchbox
  example.

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Isotopes

• All atoms of the same element have the same
  number of protons (called atomic number or z)
• Neutrons may vary, causing different masses but
  not properties
• These are called isotopes
• Thee is an optimum ratio, so many isotopes are
  unstable (radioactive)
• Carbon-12 and carbon-14 12C , 14C
• Also called a nuclide

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Atomic Mass

• Relative scale
• Mass of carbon-12 is exactly 12 amus
• All others are relative
• Mass of each nuclide is roughly P N (mass
  number)
• Periodic table mass represents kind and abundance
  of each nuclide of an element (weighted average)

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Mass Spectrometer
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Analysis
Try a problem
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Periodic Table

• Group
• Period
• Metals
• Nonmetals
• Metalloids

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Molecules

• Covalently-bonded atoms
• Two nonmetals and/or hydrogen
• Represented by a formula
• Examples

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Formulas

• Molecular formula tells exact number of atoms
  in a molecule
• C6H12O6
• Empirical Formula simplest whole number ratio
  of atoms in a compound (reduced) Glucose?

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Models

• Structural
• Perspective
• Ball-and-stick
• Space-filling

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Ions

• Most atoms readily gain or lose electrons
• Metals
• lose
• positive charge
• cation
• Nonmetals
• gain
• negative charge
• anion

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Polyatomic Ions

• Covalently bonded group of atoms carrying a
  single charge
• Nitrate, sulfate
• Learn!

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Ionic Compounds

• Formula unit is simplest ratio of ions
• Metal nonmetal
• Cross-over to predict formula
• Formula of compound from barium phosphorus

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Naming

• NaCl
• KNO3
• CoS
• N2O5

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Oxyanions

• Contain O
• End in ate or ite
• ate is most common
• ite is one oxygen less than the most common
  form
• per is one more than ate form
• hypo is one less than ite form
• Try BrO2 (4 ions)

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Adding hydrogen

• When H is added to an oxyanion, the charge is
  reduced by one and the name adds hydrogen
• Try HSO4-

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Acids

• Cl- becomes HCl - hydrochloric acid
• Ate is ic and ite is ous
• ClO3- becomes HClO3
• ClO- becomes HClO

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Organics

• Read on your own