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Why do ionic oxides form basic solutions when dissolved in water?

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Two diagrams show the three-dimensional structure of a methane molecule: panel A uses a ball-and-stick model with a central carbon atom connected to four hydrogen atoms in a tetrahedral arrangement, while panel B illustrates the bond angle of 109.5 degrees and bond length of 1.09 angstroms between carbon and hydrogen atoms. — chemical compound Methane, in which four hydrogen atoms are bound to a single carbon atom, is an example of a basic chemical compound. The structures of chemical compounds are influenced by complex factors, such as bond angles and bond length.

Ionic metal oxides form basic solutions when dissolved in water because they react to produce hydroxide ions ( $O H^{-}$ ), which are characteristic of bases.12

These compounds, which contain metal cations and oxide anions ( $O^{2 -}$ ), undergo a chemical reaction with water molecules. For example, alkali metal oxides ( $M_{2} O$ ) react according to the following equation:
$M_{2} O + H_{2} O \to 2 M O H$

Similarly, alkaline earth metal oxides ( $M O$ ) react to form metal hydroxides:
$M O + H_{2} O \to M (O H)_{2}$

Because the resulting solutions contain a higher concentration of hydroxide ions than hydronium ions ( $[O H^{-}] > [H^{+}]$ ), the solution is basic, characterized by a pH greater than 7. Due to this behavior, these ionic compounds are frequently referred to as basic oxides.13