Swollen Glandsalcohol

elements of internal transition - Lanthanides and actinides

ELEMENTS OF INTERNAL TRANSITION -
lanthanide elements and actinide elements of the block f are commonly called inner transition elements or rare earths
what you thought were not very common in nature. They consist
Two series of 14 elements and are arranged in the 6th and 7th period between the 3rd and 4th
group of the periodic table. Usually they are represented separately from other items
simply for a more meaningful representation of the periodic table itself.
The two series are also indicated by the name of the element that precedes each of them. So we will have the series of lanthanide or lanthanides (6th season) and actinides or attinoidi (7 th period). The Lanthanides

character elements are metallic, silvery-white, highly electropositive and reactive
. The atomic radii are very similar (between 1.02 and 0.86 Å). Their chemistry is so similar as to have led, until 1907, to consider a single element.
The lanthanides are all in nature, with the exception of promethium (Pm, Z = 61 and obtained synthetic), which are only found in compounds. Although it is commonly known as rare earths and nature have a certain abundance. For example, the Ce (6.6 ° 10.3% by weight in the crust; 25 th most abundant element) has an abundance similar to that of Cu and is about four times more abundant than Pb.
Actinide

character elements are metallic, silvery-white, responsive.
are all radioactive, with short relatively short half-life (except for 232Th, 235U and 238U have t ½ comparable age of the earth and are called primary source).
The only elements of the actinide series to exist in nature, even if not widespread, are Th, Pa and U.
All others have been produced synthetically by nuclear reactions.