Why is the bond between H and F in HF considered polar covalent whereas HCl, HI, and so on are all ionic? The electronegativity difference between them suggests that it too should be ionic, yet all textbooks say that HF is covalent. Is there a good reason why?
Answer
I don't think I've ever seen a reputable source claiming the bonds in HCl, HBr and HI are mainly ionic. The fact that they are all gasses at room temperature clearly suggests otherwise. HF has the most ionic character of all the hydrogen halides, but it too has a rather low boiling point (just below room temperature), which is uncharacteristic of ionic compounds.
It is best to think of all hydrogen halides as covalent polar molecules, with the polarity increasing in the order HI < HBr < HCl < HF, as suggested by the electronegativity differences.
No comments:
Post a Comment