The octet rule states that, with the exception of the innermost shell, atoms are most energetically stable when their valence shell contains:

1. This rule explains why atoms tend to gain, lose, or share electrons in predictable ways when forming bonds. 2. The text states: "This is known as the octet rule, which states, with the exception of the innermost shell, that atoms are more stable energetically when they have eight electrons in their valence shell." 3. The innermost shell is the noted exception, since it is full with just two electrons -- but for outer valence shells generally, the target is eight. 4. So the octet rule specifically points to eight electrons as the stable valence-shell configuration. _Source: OpenStax Biology Ch 2 "The Chemical Foundation of Life", p.38 §2.1 | Atoms, Isotopes, Ions, and Molecules: The Building Blocks_