[kaseli]

Hello,

I am learning about galvanic cells in my chemistry class, and one thing I don't understand is why a zinc electrode (solid bar of zinc, no net charge) when placed into a solution of Zinc 2+ ions, ionizes such that the neutral zinc atoms become Zinc 2+ ions.  I understand there are also negative ions in the solution from a Zinc salt that was dissolved initially to get the Zinc 2+ ions, but I'm not sure if that has anything to do with it.

Likewise, why does a solid bar of copper in copper ion solution ionize?  My chemistry book only states that it happens, it doesn't really explain why it happens.  I have tried looking online but cannot easily find an answer.  If someone could explain this to me, or point out any errors in my understanding/assumptions of the situation, it would be very much appreciated.

EDIT:  After reading some more online about galvanic cells and oxidation/reduction reactions in general, it seems that the solid zinc is oxidized by the zinc 2+ ions, and I can see why Zinc(s) would want to give up 2 electrons, so that it could have a complete outer shell of 10 electrons and be more stable, but then why would the Zinc 2+ accept these electrons and go to a less stable state?  Or do the electrons not go to the Zinc 2+ ion?  If they don't, then it's not an oxidation/reduction reaction, right?

My book just says "In the half-cell on the left, a zinc metal atom loses two electrons.  These flow through the zinc electrode to the external circuit, then to the copper electrode in the half-cell on the right."

How does it lose two electrons?  If it's oxidized, the electrons have to go to Zinc 2+, right?  Also, what causes the electrons to suddenly want to flow through the zinc electrode?  The electrode itself has no charge if it is made of neutral zinc atoms, so why would the electron flow through it?

Sorry for the lengthy question... I'm just so confused.

[Borek]

I wonder if you are not forgetting that the total reaction is

Cu²⁺ + Zn Cu + Zn²⁺

That is, you have two cells and for the reaction to proceed you need both cells connected and working at the same time.

Or perhaps you are looking for this kind of explanation.

Also, what causes the electrons to suddenly want to flow through the zinc electrode?

The other half cell.

The electrode itself has no charge if it is made of neutral zinc atoms, so why would the electron flow through it?

It has a small charge, see the linked post.

[kaseli]

I am still not understanding this.  Let me try asking one question at a time.

First, what is oxidizing the Zn(s) to become Zn2+(aq)?

(Please be specific and don't just say copper.  Is it Cu(s) or Cu2+(aq)?  Or is it something else?)

[408]

I am still not understanding this.  Let me try asking one question at a time.

First, what is oxidizing the Zn(s) to become Zn2+(aq)?

(Please be specific and don't just say copper.  Is it Cu(s) or Cu2+(aq)?  Or is it something else?)

You want to identify the strongest oxidizing agent (Cu2+) and strongest reducing agent (Zn)

First, do not care about the copper metal electrode, or the zinc 2+ solution.  These could be replaced by graphite and NaCl for all the cell cares.  But half cells are not defined like this so nobody talks about this fact. 

If you stuck a zinc rod in an aqueous copper (II) solution, you know what would happen, Zn->Zn2+ + 2e- and Cu2+ + 2e- -->Cu.  This cell is no different,you are just separating the reaction locations, while leaving the zinc in electric contact with the copper (II) solution via the wire and copper electrode.  Because of this electrical contact, the system is able to work towards its equilibrium state by the zinc metal sticking its electrons through the connecting wire, through the copper, and into the Cu(II) becoming Cu(O) on the other side. 

A galvanic cell simply separates the half reactions of a redox reaction, allowing the flow of electrons to do electrical work on an external system (eg. lightbulb)