# Why does the chlorine atom in hydrogen chloride acquire a slightly negative charge?

And in the $H - C l$ molecule, chlorine polarizes electron density towards itself to give a $\stackrel{+ \delta}{H} - \stackrel{\delta -}{C} l$ dipole. And in aqueous solution, the polarization goes to completion to give hydronium and chloride ions......
$\stackrel{+ \delta}{H} - \stackrel{\delta -}{C} l \stackrel{{H}_{2} O}{\rightarrow} {H}_{3} {O}^{+} + C {l}^{-}$
What we write as ${H}_{3} {O}^{+}$ is a conception only, and the actual acidium species is probably ${H}_{7} {O}_{3}^{+}$ or similar.