oxygen has six electrons in its outer shell. what is the charge on an oxide ion?

Oxygen's outer shell has six electrons, so it gains two more to form a stable oxide ion with a full octet.
The oxide ion thus carries a charge of 2-.

Why Oxygen Forms O²⁻

Neutral oxygen atoms have eight electrons total: two in the inner shell and six in the outer (valence) shell, following the electron configuration 1s² 2s² 2p⁴.

To achieve stability via the octet rule—mimicking noble gases like neon with eight valence electrons—oxygen accepts two electrons from a metal, filling its outer shell completely.

This addition of two extra electrons (beyond its eight protons) results in a net charge of -2, denoted as O²⁻.

Real-World Examples

• In magnesium oxide (MgO), Mg loses two electrons to become Mg²⁺, which oxygen gains for its O²⁻, forming a neutral ionic compound.

• Sodium oxide (Na₂O) involves two Na⁺ ions donating one electron each to one O²⁻ atom.

Common Misconceptions

• Not all oxygen is charged : Neutral O atoms (like in O₂ gas) have zero charge and six valence electrons; only ions like oxide are O²⁻.

• Oxygen rarely loses electrons (that would make O²⁺, uncommon); it prefers gaining for stability.

TL;DR: Oxide ion charge is 2- because oxygen grabs two electrons to complete its outer shell.

Information gathered from public forums or data available on the internet and portrayed here.