When magnesium reacts with oxygen to form magnesium oxide, which of the following statements is NOT correct?

The correct option is: Magnesium loses electrons to form Mg³⁺ ions.

Let us break down the reaction between magnesium and oxygen step-by-step to understand why this statement is incorrect (and therefore the correct answer to the question).

1. Electron Configuration of Magnesium:
Magnesium (Mg) is an alkaline earth metal in Group 2 of the periodic table. It has an atomic number of 12, which means a neutral magnesium atom has 12 electrons. Its electron configuration is 2, 8, 2. To achieve a stable octet (a full outer energy level like the nearest noble gas, neon), magnesium needs to lose its 2 valence electrons.

When magnesium loses these 2 valence electrons, it forms a magnesium cation with a charge of +2:
$$\mathrm{Mg}\to {\mathrm{Mg}}^{2+}+2e^{-}$$
Therefore, magnesium forms Mg²⁺ ions, not Mg³⁺ ions. This makes the statement "Magnesium loses electrons to form Mg³⁺ ions" incorrect.

2. Electron Configuration of Oxygen:
Oxygen (O) is a nonmetal in Group 16 of the periodic table. It has an atomic number of 8, meaning a neutral oxygen atom has 8 electrons. Its electron configuration is 2, 6. To achieve a stable octet (like the nearest noble gas, neon), oxygen needs to gain 2 electrons.

When oxygen gains the 2 electrons lost by magnesium, it forms an oxide anion with a charge of -2:
$$O+2e^{-}\to O^{2-}$$
Thus, the statement "Oxygen gains electrons to form O²⁻ ions" is correct.

3. Nature of the Bond:
The transfer of electrons from the magnesium metal to the oxygen nonmetal results in the formation of positively charged Mg²⁺ ions and negatively charged O^2- ions. The strong electrostatic attraction between these oppositely charged ions forms an ionic bond, resulting in the ionic compound magnesium oxide (MgO).

Thus, the statement "The compound formed contains ionic bonds" is correct.