What is the most stable oxidation state of the oxygen atom?

The correct answer is option 2. -2.

The most stable oxidation state of the oxygen atom is \(-2\).

Oxygen typically exhibits an oxidation state of -2 in most of its compounds. This is because oxygen is highly electronegative, meaning it has a strong tendency to attract electrons towards itself in chemical bonds. In most compounds, oxygen forms bonds where it gains two electrons, resulting in an oxidation state of -2.

Examples include water \((H_2O)\), carbon dioxide \((CO_2)\), and most oxides such as magnesium oxide \((MgO)\) and silicon dioxide \((SiO_2)\).

While -2 is the most common oxidation state for oxygen, there are exceptions where it can exhibit other oxidation states.

For example, in peroxides (compounds containing the peroxide ion \(O_2^{2-}\)), oxygen has an oxidation state of -1. Examples include hydrogen peroxide \((H_2O_2)\) and sodium peroxide \((Na_2O_2)\). Oxygen can also exhibit oxidation states of 0 (in elemental form \(O_2\)) and -1/2 (in superoxides such as potassium superoxide, \(KO_2\)).

The most stable oxidation state of the oxygen atom is -2, which is the most common oxidation state observed in its compounds due to its high electronegativity and tendency to gain electrons in chemical bonds.

Therefore, the correct option is -2.