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Halogens exist in different physical state

  1. Mar 17, 2005 #1
    At room temperature and atmospheric pressure, the halogens exist in different physical states. Chlorine is a gas, bromine is a liquid, and iodine is a solid. What are the boiling points and melting points for these elements? Estimate the volume of the Cl2, Br2, and I2 molecules. Comment on the effect of molecular volume on intermolecular forces. Compare and contrast the intermolecular interactions of the molecules.

    I think I can look for the boiling and melting points online.

    For the second question, do I use PV=nRT, where P=1 atm, n=1/molar mass of the gases, and T=298K? (not sure about n)

    For the 3rd and 4th question, can someone give me a hint? And does boiling and melting points relate to them in any way?

    Thank you.
  2. jcsd
  3. Mar 17, 2005 #2


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    I think increasing atomic size reduces the control of valence shell electrons by the core, thus iodine's valence electrons are more active than bromine, and so on. Solid formation involves intermolecular forces, so increased activity results in an increased rate of this kind of interaction.
  4. Mar 17, 2005 #3


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    Yeah, you can actually work out PV=nRT to find that at standard temperature and pressure 22.4L of gas corresponds to on mole of the ideal gas. You may note that some of the halogens do not exists as gases under these conditions.

    With stronger intermolecular interactions will result in higher boiling points, since higher internal energy is required to achieve separation from intermolecular attractions which are due to the respective properties of each element.
  5. Mar 17, 2005 #4


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    Volume of the molecule has nothing to do with the volume of the ideal gas. No idea what kind of estimation you should made.

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