# Why do metals form ions in solution? [closed]

I'm looking at redox half-reactions, such as the one below:

$$\ce{Zn(s) -> Zn^2+(aq) + 2 e-}$$ Does the zinc react with the water and dissociate into ions? Why doesn't solid zinc have a charge?

## closed as off-topic by Jan, Todd Minehardt, Jannis Andreska, Philipp, Geoff HutchisonNov 8 '15 at 18:40

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• How do your questions connect with half-reaction? Zinc can react with water in presence of significant amount of OH- ions, but you need second half reaction – Mithoron Oct 9 '15 at 22:43

Solids can't have a charge (neither can liquids or gases). The electrostatic forces are immensely great, way greater than you seem to think right now. Just imagine the forces that would be tearing apart a droplet of water (say, 36 microliters) if 0.001 of its molecules (not all of them, God forbid) would suddenly become positive ions. If you are aware of the Coulomb's law, you can help your imagination by actually calculating these forces.

(By now you may wonder how electrical phenomena are possible at all, but that's another story.)

Just in case if you don't like that answer, here is another:

Solid zinc, like any other metal, does have a charge. It consists of $\mathrm{Zn}^{2+}$ ions. These ions are immersed in a sea of electrons, which balances their charge, holds them together, and also is responsible for such properties typical of all metals as electrical conductivity, metallic lustre, etc.

Does the zinc react with the water and dissociate into ions?

Not by itself. You've only shown a "half-cell" reaction in a chemical reaction known as an oxidation-reduction reaction. For the reaction to take place something in the solution would also have to be oxidizing. So if you just stick a strip of zinc in distilled water, the zinc strip won't dissolve.

Why doesn't solid zinc have a charge?

The simple answer is by convention. When we say "solid zinc" we mean a macroscopic size sample of zinc. So we're saying that the whole sample isn't charged. However if you look at an individual zinc atom in the chunk of zinc, then the single atom effectively has a +2 charge and 2 electrons are in "metal conduction band" which means that the electrons are in bonding levels that allow them to conduct electricity.

If you have two metal zinc plates you can make a capacitor from them. You can then use a battery to charge one plate + and one plate -.

Another exception is a thermocouple. You have two different metals pressed together. Think of two wires fused in the middle. At the junction the two metals will develop a charge. The current will be small, but an operational amplifier can easily detect the current.