Radium (Ra) is a highly reactive alkaline earth metal that readily reacts with oxygen (O2) to form radium oxide (RaO). The reaction between radium and oxygen can be described as follows:

2Ra + O2 → 2RaO

In this reaction, radium atoms lose two valence electrons to oxygen atoms, resulting in the formation of positively charged radium ions (Ra2+) and negatively charged oxide ions (O2-). The electrostatic attraction between the radium and oxide ions leads to the formation of a stable ionic compound, radium oxide.

The reaction of radium with oxygen is highly exothermic, releasing a significant amount of heat and light. This makes radium an extremely dangerous element to handle, as it can easily ignite and cause fires or explosions. Radium also reacts vigorously with water to form radium hydroxide and hydrogen gas.

Due to its high reactivity and the associated safety risks, radium is handled and stored with extreme care in specialized facilities. It is primarily used in small quantities for medical purposes, such as radiation therapy, and in certain industrial applications, such as radiography and ionization sources.