There has to be a direct relation between metallic crystal structure formation and electrons in orbitals. For instance, we know that Fe2+ forms body centered cubic or bcc structure with the coordination number of 8, which means each Fe atom bonds with 8 others after getting rid of the two electrons in the 4S orbital.
The electron configuration of one Fe2+ would look as follows:
1s2 2s22p6 3s23p63d6
The problem is, that I do not see how Fe2+ would react with 8 others, based on the electron configuration and the octet rule, to form bcc structure.