Why are closed shells more stable?

Question

Wyatt Atkins · Accepted Answer

Closed shells are more stable because they have the highest ionisation energy in their periods.

Stability means being unreactive. The most unreactive elements are those least willing to give up an electron (or least willing to gain one). You can see from the diagram that the noble gases, with full (closed) out shells have the highest ionization energies and so have the strongest attractions for their out shell electrons, so they are least willing to transfer or share electrons.

For completeness we ought to consider electron affinity too - the energy released when an atom gains an electron. The noble gases have the lowest electron affinities so are least able to attract an additional electron into their outer shell - another way of reacting.

Cooper Adams · Answer

undefined Because closed shells represent electron configurations that satisfy the octet rule or other relevant electron configuration rules, they are more stable because they lower the overall energy state of the atom or molecule and reduce its likelihood of participating in interactions or going through chemical reactions that could upset its stable electron arrangement.