It has long been presumed that there is a common cause at the genetic, cognitive, and neural levels for autism's characteristic triad of symptoms. However, there is increasing suspicion that autism is instead a complex disorder whose core aspects have distinct causes that often co-occur.
1 Transition metals are kinds of metals that have electrons in d or f orbitals. 2  Transition metals are in columns 3-12 of the periodic table and in the lanthanide and actinide series.  Most transition metals are lustrous, silvery, hard, and good conductors; however, properties may vary greatly.
Lanthanum is a transition element in Group 3 (IIIB) of the periodic table. Lanthanum's position makes it one of the transition metals. The transition metals are found in the center of the periodic table, in Groups 3 through 12. Lanthanum can also be classified as a rare earth element. The rare earth elements are the 15 elements that make up Row 6 of the periodic table. That group of elements is also called the lanthanides.