code: def is_transition_metal(self):
          
          ns = list(range(21, 31))
          ns.extend(list(range(39, 49)))
          ns.append(57)
          ns.extend(list(range(72, 81)))
          ns.append(89)
          ns.extend(list(range(104, 113)))
          return self.Z in ns
docs: True if element is a transition metal.