Chemistry (redox reactions)

A "metal - metalion system" is also known as a "metal - metal ionhalf-cell". It is a system ofhalf-cell which is made by dipping a metal electrode into a solution of thesalt (usually the nitrate or the sulphate) of the metal, and the reaction occurringat the half-cell is the oxidation of the metal into the metal ion or the reductionthe metal ion to the metal.

For example, a "copper - copper(II) ion half-cell" can be made bydipping a copper electrode into copper(II) sulphate (or copper(II) nitrate) solution,and a "zinc - zinc ion half-cell" can be made by dipping a zincelectrode in zinc sulphate (or zinc nitrate) solution.

When a complete circuit is made by connecting the two half-cell systems with anexternal circuit and a salt bridge :
At the zinc electrode, zinc is oxidized to zinc ion :
Zn(s) →Zn^2+(aq) + 2e^-
At the copper electrode, copper(II) ion is reduced to copper ion :
Cu^2+(aq) + 2e^- → Cu(s)

2012-04-09 21:41:21 補充：
I don't understand what are you asking,
"So, does it mean the negative pole? The end that donates electrons?"