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When a molecule absorbs IR eletromagnetic energy, what are the vibrational modes affected?

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Answer:

Stretching vibration and bending vibration

Step-by-step explanation:

1. Stretching vibration results in the variation of the bond length. There are two types of stretching vibration:

  • In asymmetric bending, bonds move in and out as a result of the vibration.
  • In symmetric bending, bonds move such that the bond length either gets shorter or longer.

2. Bending vibration results in the variation of the bond angle.

These can be grouped into 4 types:

  • Rocking- It is that motion in which two atoms are in the motion like that of the motion of a pendulum of a clock.
  • Scissoring- The motion of to atoms either away from each other or towards each other.
  • Twisting- It is where the motion of the two atoms resembles that of the motion on a treadmill.
  • Wagging- It is the motion in V- shape in the back and forth direction.
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