The compound formed is AB which is ionic in nature. As we know, an ionic compound is a chemical compound in which ions are held together by electrostatic force. The electronic configuration of two elements, A and B, are 2, 8, 2 and 2, 6, respectively. From their electronic configuration, we see that A (magnesium) is a metal and B (oxygen) is a non-metal; thereby, A loses its valence electrons and forms a cation, while B accepts those electrons and forms an anion. These oppositely charged ions are drawn closer due to electrostatic forces, and an ionic compound (MgO) is formed.