Editing Octet rule (section)

{{Short description|Chemical rule of thumb}}
{{More citations needed|date=October 2023}}
[[File:Carbon-dioxide-octet-Lewis-2D.png|thumb|The bonding in [[carbon dioxide]] (CO<sub>2</sub>): all atoms are surrounded by 8 electrons, fulfilling the '''octet rule'''.]]
The '''octet rule''' is a [[chemistry|chemical]] [[rule of thumb]] that reflects the theory that [[main-group element]]s tend to [[chemical bond|bond]] in such a way that each [[atom]] has eight [[electrons]] in its [[valence shell]], giving it the same [[electron configuration|electronic configuration]] as a [[noble gas]]. The rule is especially applicable to [[carbon]], [[nitrogen]], [[oxygen]], and the [[halogens]]; although more generally the rule is applicable for the [[s-block]] and [[p-block]] of the [[periodic table]]. Other rules exist for other elements, such as the [[duplet rule]] for [[hydrogen]] and [[helium]], and the [[18-electron rule]] for [[transition metal]]s.

The valence electrons in molecules like carbon dioxide (CO₂) can be visualized using a [[Lewis structure|Lewis electron dot diagram]]. In [[Covalent bond|covalent bonds]], electrons shared between two atoms are counted toward the octet of both atoms. In carbon dioxide each oxygen shares four electrons with the central carbon, two (shown in red) from the oxygen itself and two (shown in black) from the carbon. All four of these electrons are counted in both the carbon octet and the oxygen octet, so that both atoms are considered to obey the octet rule.