In short, that chlorine atom really wants to be somewhere else, and nearly anything, even water, will break the bond. So now there's chlorine ions floating arou

In short, that chlorine atom really wants to be somewhere else, and nearly anything, even water, will break the bond. So now there's chlorine ions floating around, and chlorine has the 2nd highest electronegativity after fluorine. It's so reactive it will even form compounds with many of the noble gases.