Question

give the electronic configuration of Cu²+ and Cr³+

Answer 1

The electron configuration of the Cu atom is 1s2 2s2 2p6 3s2 3p6 3d10 4s1 
When the copper atom lose 2 electrons, Cu2+ ion is formed
It lose One electron from the 4s sub-shell, the other from the 3d sub-shell.
Therefore, electron configuration of Cu2+ is: 1s22s2 2p6 3s2 3p6 3d9 




The atomic number of Chromium is Z=24,

However, the chromium ion Cr3+ possesses 24e−−3e−=21e− due to the loss of 3 of its electrons.

Thus, the electron configuration of Cr3+is:
Cr3+:1s22s22p63s23p64s03d3