How do you turn two positive ions back to atoms?

1 Answer
Jan 14, 2017

Give them electrons.


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: #CuO + H_2 rightarrow Cu + H_2O#

Copper ions gaining electrons (reduction): #Cu^(2+) + 2e^(-) rightarrow Cu#

Providing the electrons (oxidation): #O^(2-) + H_2 rightarrow H_2O + 2e^-#