Which two ions have the same electron configuration?

a) na+ and o2- b) li+ and f- c) ca2+ and br- d) na+ and o3-

A) Na+ and O2-

Explanation:

To know the electronic configuration, one has to determine the numbers of electrons present in each atom.

Na+ means a sodium atom that has lost one valence electron. A Sodium atom  initially has 11 electrons, but having lost an electron making it 10 electrons remaining with electron configuration of 1s2 2s2 2p6.

O2- means oxygen atom that has gained two valence electrons. An oxygen atom  initially has 8 electrons, having gained two electrons makes it 10 electrons with electron configuration of 1s2 2s2 2p6. same as Na+

The purpose of gaining or losing electrons is to attain a stable duplet or octet structure.