Thorium is a chemical element in actinide group. It is a weakly radioactive metal. It has a shiny, silvery white color. It has the chemical symbol Th and the atomic number 90. Thorium is named for Thor, the Norse god of thunder. It is found in nature, especially in India, the United States, and Australia. Many scientists believe that thorium would make a good nuclear fuel because it makes much less waste and is four times as common as uranium. It makes 3,200,000 times as much energy as coal and 200 times as much energy as uranium, because natural uranium is mostly non-fissile isotopes. Scientists believe that there is enough of it to power the world for thousands of years. Natural thorium has an atomic weight of 232.