Ammonium trioxonitrate(v) is the chemical name for ammonium nitrate (NH\(_4\)NO\(_3\)). When heated under typical, moderate temperature conditions (below approximately 300°C), it undergoes a thermal decomposition reaction. The primary products of this reaction are dinitrogen monoxide (nitrous oxide,N\(_2\)O) gas and water (H\(_2\)O) vapor.

NH\(_4\)NO\(_3\) → N\(_2\)O + 2H\(_2\)O

This reaction is different from the decomposition of other metallic nitrates. Therefore, the correct answer is option A