Octet rule

Definition

The octet rule states that atoms tend to gain, lose, or share electrons in order to have a full set of eight valence electrons. This configuration is energetically favorable and resembles the electron configuration of noble gases.

5 Must Know Facts For Your Next Test

1. Atoms with fewer than eight electrons will react to achieve a full octet.
2. The octet rule explains the stability of noble gases which naturally possess a full set of valence electrons.
3. Elements in periods 1 and 2 follow the octet rule most strictly due to their smaller number of available electron shells.
4. Exceptions to the octet rule include molecules with an odd number of electrons, molecules where one or more atoms possess more or fewer than eight electrons, and transition metals.
5. The formation of ionic and covalent bonds can be explained by the octet rule as atoms transfer or share electrons to complete their outermost shells.

Review Questions

• What is the primary goal for an atom according to the octet rule?
• Which groups in the periodic table are most likely to follow the octet rule?
• Name one type of molecule that is an exception to the octet rule.

Related terms

Valence Electrons: Electrons located in an atom's outermost shell that are involved in forming bonds.

Noble Gases: Elements found in Group 18 of the periodic table that naturally have a complete set of eight valence electrons.

Ionic Bonding: A type of chemical bond where atoms transfer electrons to achieve full outer shells and form ions.