Potassium (K) forms several oxides, but \( K_2O_3 \) does not exist due to the instability of such an oxide. The common oxides of potassium are:
\( K_2O \) (Potassium oxide)
\( KO_2 \) (Potassium superoxide)
\( K_2O_2 \) (Potassium peroxide)
These oxides are stable under normal conditions. \( K_2O_3 \), on the other hand, is not stable and does not exist. This is due to the fact that potassium typically forms compounds with an oxidation state of +1 or +2, and an oxide like \( K_2O_3 \) would require a higher oxidation state, which is not stable for potassium. Thus, the oxide of potassium that does not exist is \( K_2O_3 \).
The correct option is (A): \(K_2O_3\)
Ethanal to But-2-enal