# How many electrons are lost or gained in forming each Cu^(2+)?

$C u \rightarrow C {u}^{2 +} + 2 {e}^{-}$
Suppose you knew nothing about chemistry, but something about physics and electrical charge. You know that if something is neutral then it has an equal number of positive and negative charges. In the reaction above, we started with a neutral atom (copper metal), and upon (so-called) oxidation we finished with a cupric ion, $C {u}^{2 +}$. From charge considerations alone (even if we knew nothing about electrons), we must have removed 2 negatively charged particles. Of course, these species are electrons.