Question about Faraday's 2nd Law of electrolysis?

Question

Faraday's 2nd Law of electrolysis is this: "The number of Faradays of electric charge required to discharge one mole of substance at an electrode is equal to the number of "excess" elementary charges on that ion."

But don't understand, esp the phrase 'the number of "excess" elementary charges on that ion'. Can sb please kindly explain it to me? Thanks!!!!

Answer 1

This is old-fashioned language. It means "ionic charge". Thus a mole of Cu2+ requires 2 Faradays to reduce it to a mole of copper metal.