Do ions still "conduct electricity" if a physical connection made by aqueous electrolytes between the anode and the cathode is nonexistent?

Question

I always had the misconception that when people say ions conduct electricity, what they actually mean is a connection is made between the cathode and the anode by the ions and electrons can flow from the cathode to the anode through this connection.

However, I recently learned that ions conduct electricity because chemical reactions are happening around the electrodes.

Taking the example of the electrolysis of sodium chloride water solution. At the cathode, $\ce{Na+}$ captures electron ($\ce{Na+ + e- -> Na}$); at the anode, $\ce{Cl-}$ releases electron ($\ce{2Cl- -> Cl2 + 2e-}$). And this is because the battery takes electrons from the anode and feeds electrons to the cathode, and positively charged anode attracts anions and negatively charged cathode attracts cations. That is to say electrons do not flow from cathode to anode but are given to and taken from the ions.

I still feel confused after knowing this explanation because it seems to me that the anode and the cathode do not need to be connected by aqueous electrolytes to "conduct electricity". Suppose the cathode and the anode are placed into different solutions in different containers, anode still attracts anions and cathode still attracts cations. So that there should still be electricity flowing through the circuit.

Some people say that a "closed circuit" is required for ions to conduct electricity. If that is the case then what am I missing here?

Answer 1

If a cathode (negative pole) is placed alone in an ionic solution (without any anode in the solution), it will attract cations from the solution, and discharge maybe one or two or one thousand of these cations. This will last maybe 1 nanosecond, and then it will stop. The reason is that this number of atoms is extremely small, so small that the neutral atoms which are deposited on the cathode cannot be seen or weighed. And then the cathodic discharge will stop, because the whole solution has lost positive charges (cations), but has not lost any negative charges (anions). As a consequence, the whole solution becomes negatively charged. This negative charge increases with the time and prevents the cathode from bringing new electrons necessary for discharging further cations. The electrolysis will stop. The electrode is said to be "polarized".

Answer 2

I want to further expound upon your newly developed misconception as written in your comments although Maurice has already explained it well.

I see what I'm overlooking here. So what happens is that the solution can become charged to create an electric field that cancels out the electrodes' ability to attract ions, therefore preventing chemical reactions, unless the solution is able to remain neutrally charged.

No the bulk solution has to remain neutral all the time. There can be no charge build up in the electrolytic cell. Everything takes place at the interface of the dipping electrode and the solution next to it.

By definition, whenever electricity will pass through an electrically conducting solution, chemical reactions will take place. "Something" has to oxidize at the anode and "something" has to reduce at the cathode. That something could be the solvent, neutral molecules, ions or anything in the solution. Something has to lose electrons and something has to gain electrons.

I think you are looking for the right words, because it seems your confusion arises from the semantics. Ions carry electric charge, and rate of movement of charges constitutes current. Therefore, we say that nature of current in a solution is ionic current.

Suppose the cathode and the anode are placed into different solutions in different containers, anode still attracts anions and cathode still attracts cations. So that there should still be electricity flowing through the circuit.

Yes, do you recall a capacitor which are two disconnected plates of metal. When it is connected to a battery, quickly a small amount of current flow. It it is exactly like this scenario. It may be called as capacitive current.

Now remember that capacitors in a circuit do not allow direct current to pass through it. Similarly two separated electrodes sitting in two beakers will not allow direct current to pass in the external circuit.

Some people say that a "closed circuit" is required for ions to conduct electricity. If that is the case then what am I missing here?

Now this is a different situation. When you want the direct current to flow, then yes, the circuit has to be closed. Think of a battery as a recycling pump. Imagine a pump in your house, which fills up a water tank placed on the roof of your house, and this tank is connected to your faucets, and all that water you use is pumped back into the water tank. Dirty analogy but good for a battery.