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What is the octet rule?

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Quick answer

The octet rule is the chemistry guideline that atoms tend to gain, lose, or share electrons to end up with eight in their outer shell. That full outer shell is especially stable, which is why atoms bond the way they do.

Key things to understand

  1. Atoms 'want' a full outer shell of eight electrons.
  2. They achieve it by sharing, gaining, or losing electrons.
  3. This drive explains why and how atoms form bonds.
  4. Noble gases already have full shells, so they rarely react.
  5. There are exceptions, like hydrogen (which seeks two).

People also ask

Why do atoms follow the octet rule?
A full outer shell of eight electrons is a low-energy, stable arrangement, so atoms bond in ways that reach it.
What is an example of the octet rule?
Sodium gives up one electron and chlorine gains one, so both reach full shells — forming stable table salt (NaCl).
Are there exceptions to the octet rule?
Yes — hydrogen and helium aim for two electrons, and some atoms like boron or sulfur can be stable with fewer or more than eight.