Final answer:
The isoelectronic pair among the given species is O²⁻ and F, both achieving the electron configuration of neon (Ne) with 1s²2s²2p¶. The correct answer is option B.
Step-by-step explanation:
Atoms and ions that have the same number of electrons and thereby the same electronic configuration are known as isoelectronic species. Considering the given options, the correct answer to which of these species make an isoelectronic pair is O²⁻ and F.
After completing their valence shells, these two have the same electron configuration of neon (Ne), which is 1s²2s²2p¶. For instance, the fluoride ion (F-) gains one electron to complete its valence shell, resembling the neon configuration.
Similarly, the oxide ion (O²⁻) gains two electrons to achieve the same configuration. Atoms and ions that have the same electron configuration are isoelectronic, and the number of protons determines their size.