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Modes of Vibration in Greenhouse Gas Molecules


A micro-lecture that describes the vibrational modes of polyatomic molecules, how these modes determine whether the molecules are IR inactive or IR active and explains why most IR active polyatomic gas molecules are greenhouse gases.

Students will learn about the various modes of vibration in polyatomic gas molecules and the development of a charge imbalance (electrical dipole) in molecules due to the asymmetrical stretching or bending modes of vibration. This results in the absorption of heat energy from incident IR radiation in gas molecules such as carbon dioxide (CO2), water vapour, and methane (CH4) causing them to behave as greenhouse gases.

Use this tool to help your students find answers to:

  1. What happens when a molecule absorbs IR light?
  2. What determines whether a polyatomic molecule is IR active or IR inactive?
About Tool
Tool Name Greenhouse Gases
Discipline Chemistry
Topic(s) in Discipline Carbon Chemistry, Environmental Chemistry, Molecular Structure of Compounds, The Electromagnetic Spectrum, Infrared (IR) Spectroscopy, Molecular Vibration, Vibrational Modes, IR Active Molecule, IR Absorption and Greenhouse Gases, Greenhouse Effect, Stretching and Bending Modes of Vibration
Climate Topic Climate and the Atmosphere, Greenhouse Effect
Type of tool Video
Grade Level Undergraduate
Location Global
Language English
Translation      –
Developed by Prof David Archer, University of Chicago
Hosted at Kaltura Network
Access Online
Computer Skills Basic


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