How is radioactive dating done
The prevailing view that dominated early research into transuranics was that they were regular elements in the 7th period, with thorium, protactinium and uranium corresponding to 6th-period hafnium, tantalum and tungsten, respectively.
All actinides are radioactive and release energy upon radioactive decay; naturally occurring uranium and thorium, and synthetically produced plutonium are the most abundant actinides on Earth.
All but one of the actinides are f-block elements, with the exception being either actinium or lawrencium.
The series mostly corresponds to the filling of the 5f electron shell, although actinium and thorium lack any f-electrons, and curium and lawrencium have the same number as the preceding element.
The actinide series derives its name from the first element in the series, actinium.
The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide.