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How does oxygen form an ionic compound with magnesium?

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Periodic table of the elements with color-coded categories and labeled element groups, showing atomic numbers, symbols, and basic information for each chemical element. — periodic table Modern version of the periodic table of the elements. To learn an element's name, atomic number, electron configuration, atomic weight, and more, select one from the table.

Magnesium forms an ionic compound with oxygen through the transfer of electrons, a process driven by the atoms' positions in the periodic table.

Ion Formation: Magnesium, an alkaline earth metal, has two valence electrons in its outermost shell. To achieve a stable configuration, it loses these two electrons to become a positively charged cation ( $M g^{2 +}$ ).12
Electron Transfer: Oxygen, located in group VIA, requires two additional electrons to fill its outer shell. It gains the two electrons lost by the magnesium atom, becoming a negatively charged anion ( $O^{2 -}$ ).12
Ionic Bonding: Once these oppositely charged ions are formed, the electrostatic force of attraction between them holds the atoms together in an ionic lattice structure, resulting in the compound magnesium oxide (MgO).13

This reaction is energetically favorable because the high lattice energy produced by the small, highly charged ions compensates for the energy required to form the $O^{2 -}$ ion.4