Elements in group 16 wants to bond with elements in group IIA, the group of alkaline earth metals.
The bonding will make it easier for them complete their octet.
Elements in group 16 has 6 valence electrons.
To have a complete octet, they require 2 more electrons.
Group II elements are willing donors as they are metals.
For Group II elements to fill their octets, they must lose two electrons.
So the willingness of group II elements to lose two electrons and the readiness for group 16 elements to gain the electrons makes the desire one another.
