Atoms prefer to have a filled outermost shell because this makes them more
Answer Atoms prefer to have a filled outermost shell because this makes them more stable. Atoms react with each other to get the most stable state possible. A filled outermost shell (a complete octet for s- and p-elements) is very stable because all orbitals are filled with electrons. Stability of an atom is connected with its energy. Atoms with greater stability have less energy. We can see this in chemical reactions: a reaction that increases the stability of the atoms will release energy in the form of heat or light.