The octet rule states that atoms tend to gain, lose, or share electrons until they are surrounded by eight valence electrons, matching the stable configuration of a noble gas. It is a useful guide for drawing Lewis structures and predicting formulas. The rule has exceptions, however, such as hydrogen, which is stable with two electrons, and atoms that can expand their octet.

八隅体规则指出,原子倾向于通过得失或共享电子,直至其周围有八个价电子,从而与稀有气体的稳定组态相同。它是绘制路易斯结构和预测化学式的有用指引。但该规则有例外,如氢以两个电子即稳定,以及某些可扩展八隅体的原子。