Ian,
you need to brush up a little on your chemistry, I'm afraid.
1) Calcium Carbonate is CaCO3 2) CaCO3 is ionic, so talking about 'molecules' of CaCO3 is not correct 3) Chlorine gas is molecular - Cl2. It won't be monatomic in air in normal conditions 4) The reaction equation implied by your statements is not CaCl2 + CO2 => CaCO2 + Cl2Calcium Chloride is hygroscopic, such that it will absorb water from normal atmospheres to the extent of dissolving itself - and the the solution produced continues to absorb water. In solution it will be ionic. Ths is actually an equilibrium process - at some point the solution will be dilute enough to not absorb any more water from the atmosphere.
Carbon Dioxide also dissolves in water producing 'carbonic acid' - another equilibrium process whereby there will also be carbonate and hygrogen carbonate ions in solution. There is also another equilibrium process between solid calcium carbonate and calcium carbonate in solution (as a mixture of the carbonate and hydrogen carbonate).
One thing is certain, though - chlorine gas is not evolved by the solution.
To a certain extent, all chemical reactions can be regarded as equilibrium reactions. However, with most of them, the equilibrium lies so far over to one side (so to speak) that it is a useful shorthand to say that reactants are transformed into products.
Sid