Look up: thorium-228

1. 
   thorium-228
   [n] - radioactive isotope of thorium with mass number 228
   Found on http://www.webdictionary.co.uk/definitio
   
   
2. 
   thorium-228
   radiothorium noun radioactive isotope of thorium with mass number 228
   Found on http://wordnet.princeton.edu/perl/webwn?
   
   
3. 
   Thorium-228
   `Thorium-228` is an isotope of thorium which has 90 electrons and protons and 138 neutrons. It has a half life of 1.9116 years. It is highly unstable and is not found in nature. When it decays, it emits an alpha particle and turns into Radium-224. Occasionally it decays by the unusual route of cluster decay, emitting a nucleus of oxygen-20. Th-228 has an atomic weight of 228.0287411 grams/mole. Uranium-232 decays to this nuclide by alpha emissi...
   Found on http://en.wikipedia.org/wiki/Thorium-228