# Oxidation state of Cu

If copper has 1 valence electron in the 4s subshell, how is it able to form Cu2+ with oxidation state of 2? I know the energy level difference between the 3d and 4s subshells has a part to play here, but I can't seem to put my finger on it.

• What makes you think electron cannot leave from 3d orbitals? – Arishta Mar 10 '17 at 16:00

lets just put it like this.....you wouldn't be too excited to be without your parents.....and wouldn't be really stabilised in their absence.....but put forward a condition..like you get 6-7 of your best friends to stay with you all the while they're away.....now that is good enough compensation for your parents being away for a period of time....similarly....water....surrounds the $\ce{Cu^2+}$ ion...and stabilises it through hydration...as $\ce{Cu+}$ has a much higher hydration enthalpy that $\ce{Cu+}$....it gets stabilised..and is ready to lose that last electron..though left configurationally unstable

• What do you mean by "configurationally unstable"? Is that distinct from energetic stability? – Jonathan Smith Mar 14 '17 at 13:39
• what i referred to by "configurationally unstable" is that it lacks the fully filled d orbital configuration @JonathanSmith – Supernova Mar 14 '17 at 14:51