What does the octet rule in chemistry state?

The octet rule in chemistry states that atoms tend to bond in such a way as to achieve a full outer electron shell, typically consisting of eight electrons. This preference for a complete outer shell is motivated by the stability it provides; elements with full valence shells are generally more stable than those that are not.

For most main-group elements, achieving this stable configuration often involves gaining, losing, or sharing electrons through various types of chemical bonds. For example, sodium, which has one electron in its outer shell, can lose that electron to achieve the electron configuration of neon, a noble gas, while chlorine can gain an electron to also reach a full outer shell. This tendency for atoms to bond until they have eight electrons in their outer shell is foundational in understanding chemical reactivity and the formation of compounds.

Understanding the octet rule helps explain why certain elements behave the way they do in reactions and how they form ions and molecules, making it a central principle in introductory chemistry.