What is the electron configuration for the O2- ion?

The electron configuration for the O^2- ion is 1s² 2s² 2p⁶.

To explain, an oxygen atom (O) has an atomic number of 8, which means it has 8 electrons in its neutral state. The electron configuration for a neutral oxygen atom is 1s² 2s² 2p⁴, indicating that it has 2 electrons in the first energy level (1s) and 6 electrons in the second energy level (2s and 2p combined).

When oxygen gains an additional 2 electrons to form the O^2- ion, it achieves a full outer shell. This means it now has a total of 10 electrons. The full configuration for the O^2- ion reflects this, resulting in 1s² 2s² 2p⁶, which is identical to the electron configuration of neon (Ne), making O^2- isoelectronic with Ne.