Question

how Cu is differ from Cu2+

Answer 1

because it's electronic configuration is different in both

Answer 2

Explanation:

When we write copper as only Cu then it denotes the ground state of copper. Atomic number of Cu is 29 and its electronic configuration is as follows.

     $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{10}$

Whereas $Cu^{2+}$ is the cationic form of copper. Due to the loss of 2 electrons Cu has acquired a charge of 2+. Therefore, electronic configuration of $Cu^{2+}$ is as follows.

     $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{0}3d^{9}$