* Thorium(IV) oxide (ThO₂) : This is the most stable and commonly encountered oxide of thorium. It is a white, refractory solid with a high melting point.

* Thorium(II) oxide (ThO): This oxide is less common and is not as well-characterized as thorium(IV) oxide. It is a black solid and is unstable in air, readily oxidizing to thorium(IV) oxide.

Important Note: Thorium is radioactive and its oxides are considered hazardous. It's essential to handle them with extreme caution in a controlled laboratory environment.