Thorium metal belongs to the Actinides family.
Thorium metal by far is the most stable and frequent actinoid, the half-life of 232Th is 14 billion years. In pure form Thorium is a silvery metal and it is chemically reactive and light toxic. However, its weak radioactivity can become dangerous, if it is inhaled. Therefore thorium metal is not longer much used for mantles in gas lights, which it was for a long time.Thorium metal is used for some special alloys and in good camera lenses (as ThO2). Finally thorium decays to radium.