The Dance of the Molecule: An Introduction to Molecular Motion

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The Dance of the MoleculeAn Introduction to
Molecular Motion
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Lets examine the three types of motion possible
for a molecule. We will do this in a
two-dimensional fashion however, remember this
is a three-dimensional phenomenon.
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Translational motion
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Rotational motion with translational motion
only rotational motion
translation
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Vibrational motion
Stretching of the bond between the atoms
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Vibrational motion
Bending of the bond between the atoms
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Describe the types of motion

• Translational
• Rotational
• Vibrational

whole atom or molecule changes its location in
three dimensional space
Motion of whole molecule
whole molecule spins around an axis in three
dimensional space
? Motion within molecule
motion that changes the shape of the molecule
stretching, bending, and rotation of bonds
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Some questions to ponder
In a container of gaseous helium atoms, what type
of motion would you observe?
In a container of gaseous nitrogen molecules,
what type of motion would you observe?
What is the difference between internal bond
rotation and overall rotation?
What about the motion of atoms or ions in solids?
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Consequences of motion

• What type of motion is responsible for
  collisions?
• What type of motion is responsible for changing
  the orientation of a molecule for an effective
  collision?
• Are bond angles and bond lengths constant in a
  molecule?
• What type of motion is responsible for changing
  the dipole of a molecule?

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Collisions and the Possibility of Reaction
Collisions cause directional changes
What is the path of a single atom in a vast
number of atoms?
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The torturous path is due to numerous collisions
with other atoms.
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Collisions cause reaction
This is an effective collision.