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 have the following properties in common: 1  they form coloured compounds. 2  they are good conductors of heat and electricity. 3  they can be hammered or bent into shape easily.  they are less reactive than alkali metals such as 1  sodium. they have high melting points - but mercury is a liquid at room temperature.