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.
1 They are paramagnetic. 2  The transition metal group is called the d-block of the periodic table. 3  There are 35 elements located in the d-block. 4  Sometimes the elements of column twelve of the periodic table (zinc, cadmium, mercury, copernicium) are not included as part of the transition metal group.