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    which of the following absorb radiation and why?
    H2O
    N2
    CH4
    O2
    CO2
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    (Original post by upthegunners)
    which of the following absorb radiation and why?
    H2O
    N2
    CH4
    O2
    CO2
    I know what you're trying to ask, but it isn't what you actually asked.

    All of them have bonds which can absorp energy and move to an excited state.

    However, I expect the question you meant to ask was 'which of these will have peaks on an IR spectrum?'. The reason for the distinction is that IR vibrational spectroscopy will only detect bonds where the vibration causes a change in the dipole moment. This means that homonuclear diatomics (N2, O2 etc) do not appear as the dipole stays in the same place when they vibrate.

    I would expect all the others will have vibrational modes where the dipole moment changes (been a while since I've done any of this), but you need complicated group theory in order to know how many peaks there will be.
 
 
 
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