posted by d on .
Which of the following properties increase with increasing atomic number for fluorine and chlorine?
I. melting point of the elements (yes)
II. boiling point of the hydrogen halides
i'm not sure about II because HF has the highest boiling point but fluorine and chloride fit in the general trend that increasing atomic number results in increasing boiling points. help? Is it both, just one, or neither?
In the series HI, HBr, HCl, HF, the boiling point decreases because the molar mass is decreasing; however, HF (remember F has the highest electronegativity of any element) has hydrogen bond which RAISES the boiling point of HF. H2O, NH3, HF are in the same category. HF should be a gas, H2O should be a gas but they aren't because of H bonding. NH3 IS a gas BUT the boiling point is much higher than it should be (from the trend) SbH3, AsH3, PH3, NH3.
Which answer is it then? I feel like it's just I because HF is an exception.