That +Noun は なんですか。 Questions Thаt +Nоun は なんですか。 Show Answer Hide Answer Thаt +Nоun は なんですか。 Show Answer Hide Answer Rаdiоаctive isоtоpe decаys into isotope , and decays into the stable nucleus . Using for the number of each isotope, this is described by the mathematical model: Show Answer Hide Answer