HF (Fluorine - reliably weird)

From Molecule of the Day

HF is just that, H-F, or a hydrogen bound to a fluorine. All the other acids in this group - HCl, HBr, HI - are gases. What we call "hydrochloric acid" is HCl in water, "hydrofluoric acid" is HF in water, etc. What's interesting, though, is that HCl, HBr, and HI are all strong acids - if you dissolve some in water, it will completely dissociate into H⁺ and Cl^- (for example). HF doesn't do that, and that makes it unique.

While hydrochloric acid is strong stuff, it's not even on the most-dangerous-compounds-we-use radar. If you spill some on your hands, you wash it away. It's just protons and chloride ion, neither of which are that nasty. Besides, they're ions, which don't penetrate skin well.

HF, however, isn't completely ionized, so it CAN penetrate skin. Once it's inside you, though, it can ionize, and fluorine ion is plenty toxic. It can react with some ions that are important to you, well, staying alive - like Mg²⁺ and Ca²⁺. Apparently it has an anaesthetic effect, masking potential toxicity.

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