What happens to the H electron during acid reaction?
The electron belonging to elemental hydrogen forms part of a covalent bond with $\ce{X}$. In this acid-base reaction the $\ce{HX}$ bond breaks heterolytically, meaning that both electrons constituting the bond go to $\ce{X-}$, hence the negative charge.



The base then donates electrons to the proton, forming the electron deficient species $\ce{HB+}$.