Main Profile

At A Glance

A.3.3 Explain what occurs at a molecular level during absorption of IR by molecules IB Chemistry SL

A.3.3 Explain what occurs at a molecular level during the absorption of IR radiation by molecules. If a molecule has a moving dipole when it vibrates then it will be IR active. For bent molecules (water, sulphur dioxide, -CH2-) there are 3 vibration modes you need to know and ALL of them are IR active since the dipole moves during vibration. Modes are: Asymmetrical stretching (imagine punching your own chin with alternate fists)Symmetrical stretching (punch your chin with both fists at the same time)Bending (bang your knuckles together beneath your chin)For many linear molecules (eg CO2) one mode is IR INACTIVE (the IB love this) -- the vibration does not move the dipole = symmetrical stretching.Asymmetrical stretching (imagine slapping your own ears left, right,left, right with both hands)Symmetrical stretching (slap your ears together)Bending (down stroke your ears)Hmm not sure this is helpful ...
Length: 01:09

Contact

Questions about A.3.3 Explain what occurs at a molecular level during absorption of IR by molecules IB Chemistry SL

Want more info about A.3.3 Explain what occurs at a molecular level during absorption of IR by molecules IB Chemistry SL? Get free advice from education experts and Noodle community members.

  • Answer

Ask a New Question