The Dance of the Molecule: An Introduction to Molecular Motion

1. The Dance of the Molecule:An Introduction to Molecular Motion

2. Let’s 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. This presentation MUST be viewed in PowerPoint XP.

3. Translational motion

4. Rotational motion with translational motion translation only rotational motion

5. Vibrational motion Stretching of the bond between the atoms

6. Vibrational motion Bending of the bond between the atoms

7. 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

8. 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?

9. 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?

10. Collisions and the Possibility of Reaction Collisions cause directional changes What is the path of a single atom in a vast number of atoms?

11. The torturous path is due to numerous collisions with other atoms.

12. Collisions cause reaction This is an effective collision.