# How do you turn two positive ions back to atoms?

Jan 14, 2017

Give them electrons.

#### Explanation:

Positive ions are formed when atoms (usually metals) lose electrons. This may be during a reaction, or as a result of electrolysis. To turn the positively charged ions back into atoms we have to find a way of giving them the exact number of electrons they lost. This too might be done by electrolysis, or by reacting them with a substance that could donate the electrons they need.

For example, the copper ions in copper(II) oxide CuO can be turned back into copper atoms by heating the copper(II) oxide in a stream of hydrogen gas. The hydrogen provides the electrons that are needed in this reaction as they form bonds to the oxide ion:

Overall: $C u O + {H}_{2} \rightarrow C u + {H}_{2} O$

Copper ions gaining electrons (reduction): $C {u}^{2 +} + 2 {e}^{-} \rightarrow C u$

Providing the electrons (oxidation): ${O}^{2 -} + {H}_{2} \rightarrow {H}_{2} O + 2 {e}^{-}$