Answer: oxygen
Explanation:
An ionic compound is formed when one element completely transfers its valence electron to another element.
The element which donates the electron is known as electropositive element and forms a positively charged ion called as cation. The element which accepts the electrons is known as electronegative element and forms a negatively charged ion called as anion.
As alkaline earth metal can lose two electrons, it will combine with an element which can gain electrons.
[tex]O:8:1s^22s^22p^4[/tex]
[tex]O^{2-}:10:1s^22s^22p^6[/tex]
Thus alkaline earth metal MOSTLY LIKELY combine with oxygen.
