Chapter 4: Atomic Structure

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Chapter 4 Atomic Structure
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4.1 4.2 Defining the Atom - Structure of the
Atom
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Atoms are composed of three subatomic particles

• Protons
• Neutrons
• Electrons

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Democritus ??
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Dalton??
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Thomson???
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http//highered.mcgraw-hill.com/sites/0072512644/s
tudent_view0/chapter2/animations_center.html http
//www.chem.uiuc.edu/clcwebsite/video/Cath.mov
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Millikan??
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http//highered.mcgraw-hill.com/sites/0072512644/s
tudent_view0/chapter2/animations_center.html
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Goldstein??
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Chadwick??
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A neutron walked into a bar and asked for the
price of a drink. "For you," the bartender
replied "no charge."
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To Summarize
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The Atomic Nucleus
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Thomsons Plum Pudding Model of the Atom

• electrons were stuck
• into a lump of
• positive charge,
• similar to raisins
• stuck in dough

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Rutherford??
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http//www.mhhe.com/physsci/chemistry/animations/c
hang_2e/rutherfords_experiment.swf
http//video.google.com/videoplay?docid-373655659
0151314279qrutherfordgoldfoilexperimenthlen
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Plum Pudding vs. Rutherfords
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Rutherfords Nuclear Atom

• the protons and neutrons are located in the
  nucleus
• The electrons are distributed around the nucleus
  and occupy almost all the volume of the atom.
• the nucleus is tiny compared with the atom as a
  whole.
• If an atom were the size of a football stadium,
  the nucleus would be about the size of a marble.

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Chapter 4.3 Distinguishing Among Atoms

• A grocery store might sell three varieties of
  apples Granny Smith, Red Delicious, and Golden
  Delicious. Apple varieties can differ in color,
  size, texture, aroma, and taste. Just as apples
  come in different varieties, a chemical element
  can come in different varieties called
  isotopes.

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I. Atomic Numbers
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Elements are different because they contain
different numbers of protons.

• The atomic number of an element is the number of
  protons in the nucleus of an atom of that
  element.
• atoms are electrically neutral.
• the number of electrons (negatively charged
  particles) must equal the number of protons
  (positively charged particles).

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Atoms of the First Ten Elements
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Atomic number

• Tells you the number of protons in an atom
• Every element has a unique atomic number
• Atomic number can be found on the periodic table.
  It is a whole number.

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Examples

• Nitrogen
• 7
• Hydrogen
• 1
• Oxygen
• 8
• Lead
• 82

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• You can use atomic number and the charge on the
  atom to determine the number of electrons.
• If an atom is neutral, the of electrons the
  of protons
• How many electrons and protons do each of the
  following neutrally charged atoms have ??
• protons electrons
• Zinc?
• 30 30
• Gold?
• 79 79
• Chlorine?
• 17 17
• Copper?
• 29 29
• Tin?
• 50 50

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II. Mass Number
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• The total number of protons and neutrons in an
  atom is called the mass number.
• Because the atomic number equals the number of
  protons, which equals the number of electrons (in
  a neutral atom), an oxygen atom has eight protons
  and eight electrons.
• The mass number of oxygen is equal to the number
  of protons plus the number of neutrons.
• The oxygen atom, then, has eight neutrons, which
  is the difference between the mass number and the
  atomic number (16 - 8  8).  
• The number of neutrons in an atom is the
  difference between the mass number and atomic
  number.

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Complete Chemical Symbol

• The composition of any atom can be represented in
  shorthand notation using atomic number and mass
  number
• The chemical symbol Au appears with two numbers
  written to its left.
• The atomic number is the subscript.
• The mass number is the superscript.
• You can also refer to atoms by using the mass
  number and the name of the element.
• For example gold - 197

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4
4
5
10
10
10
11
11
12
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III. Isotopes
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• How do these atoms differ ?
• All have the same number of protons (10) and
  electrons (10), but they each have different
  numbers of neutrons.
• Isotopes are atoms that have the same number of
  protons but different numbers of neutrons.  
• Because isotopes of an element have different
  numbers of neutrons, they also have different
  mass numbers.

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Isotopes of Hydrogen
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HW page 111 PP 15 16page 112 PP 17
18page 113 PP 19 20page 119 Section Assess
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