Electron structure of oxygen

A neutral oxygen atom has eight electrons. Its ground-state electron configuration is 1s² 2s² 2p⁴. In a simplified shell model, that is two electrons in the first shell and six in the second.

Meaning and context

The six outer-shell electrons are oxygen’s valence electrons in the usual introductory description. An oxide ion, O²⁻, has gained two electrons and therefore has ten electrons, with configuration 1s² 2s² 2p⁶.

Examples and usage

The proton count remains eight when the atom becomes an oxide ion. Gaining electrons changes the charge, not the element’s identity. An isotope change instead concerns the neutron count.

What to check

Keep O, O²⁻, and O₂ distinct. They represent an atom, an ion, and a molecule. A diagram or configuration for one is not automatically the correct explanation for the others.

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