1. Radioactivity: Plutonium is a radioactive element, meaning its atoms undergo radioactive decay, emitting particles and energy. This decay process is a defining characteristic of plutonium and is responsible for its hazardous nature.

2. Reacts with oxygen: Plutonium readily reacts with oxygen to form oxides. This reaction occurs quickly in air, forming a protective oxide layer on the surface of plutonium metal. This oxide layer is relatively stable and helps prevent further oxidation. However, in the presence of moisture or other oxidizing agents, plutonium can undergo further reactions, leading to the formation of various plutonium oxides and hydroxides.