Question

It is difficult to obtain oxidation state greater then two for copper..

Answer 1

Explanation:

After removal of two electrons they will have fully filled d-orbitals which acquires extra stability,so it is difficult to obtain oxidation state greater than 2 for Cu,Niand Zn.

Answer 2

Explanation:

1. As we know copper (Cu) having atomic number 29 and electronic configuration [Ar] $4s^{1} 3d^{10}$.
2. After first two oxidation state there is a high value of third ionization enthalpy due to extra stability in $Cu^{+2}$ oxidation state.
3. Hence, it's difficult to obtain oxidation state greater than two for copper.