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.
The transition metals. The transition elements are those in the middle section of the Periodic Table. All the transition elements are metals and so they have typical metallic properties-they conduct heat and electricity, they are malleable and ductile and they form positive ions when they react with non-metals.The compounds of transition metals are often coloured.he elements in the middle section of the Periodic Table are the transition elements. They're all metals with typical metallic properties eg conducting heat and electricity. They often form coloured compounds.