Which of the following is NOT a neutral oxide?

Na₂O

The correct answer is option 2. Na₂O.

Among the listed options, the oxide that is NOT neutral is \(Na_2O\) (Sodium oxide)

Neutral oxides do not exhibit acidic or basic properties when dissolved in water. They form neutral solutions.

\(Na_2O\) (sodium oxide) is categorized as a basic oxide. When it reacts with water, it forms a basic solution (sodium hydroxide, \(NaOH\)).

Here's a summary of the remaining options:

\(N_2O\) (nitrous oxide): This is a neutral oxide.

\(NO\) (nitric oxide): This is also a neutral oxide.

\(CO\) (carbon monoxide): This is another example of a neutral oxide.

Therefore, only \(Na_2O\) exhibits basic properties, making it the non-neutral oxide in the given choices.