Cobalt (Co), element with atomic number 27, has the following electronic configuration for its neutral state:\[\text{Co}: [Ar] 3d^7 4s^2.\]When cobalt forms a +2 oxidation state, it loses two electrons from the 4s orbital, resulting in the configuration:\[\text{Co}^{2+}: [Ar] 3d^7.\]The 3d subshell, capable of holding 10 electrons, is configured as \( 3d^7 \), indicating the presence of 3 unpaired electrons.