Isotopes

It is a rare oxygen isotope that has 12 more neutrons than oxygen-16, the most common form of oxygen on the planet

Authorities issued an alert for several Mexican states April 15 after thieves snatched potentially deadly radioactive material used for industrial radiography.
      
The iridium-192 source, marked X-571, was inside a container when it was stolen on Monday from a truck in Cardenas, a town in southern Tabasco state, the interior ministry said in a statement.