* Chlorine is a gas at room temperature. It exists as a yellow-green gas and would immediately evaporate if you tried to hammer it.
* Chlorine is highly reactive. It would react violently with the hammer, potentially causing a dangerous explosion.
* Chlorine is toxic. Even if you could somehow handle it, inhaling chlorine gas is extremely dangerous.
In short, you can't hammer chlorine into shape because it's a gas that's too reactive and dangerous to work with in this way.
