How many elements are there in lanthanide and Actinide series? My big doubt is does the 57th element Lanthanum and 89th element Actinium include in it? Click for the question I got

In some periodic table the entire 57-71 is given outside the box but in some of them only 58-71 is given outside the box.


The arrangement of elements in periodic table is a subject of debate. There is no particular arrangement which is the best. This is the reason of confusion.

However, Concise Inorganic Chemistry by J.D. Lee mentions:

These four elements [Sc,Y,La,Ac] are sometimes grouped with the 14 lanthanides and called collectively the 'rare-earths'. This is a misnomer because the scandium group are d-block elements and the lanthanides are f-block elements.

Pg 677, Concise Inorganic Chemistry, J.D. Lee, Blackwell Science Ltd, 1996.

So you can consider that the lanthanide and actinide group each contains 14 elements and Lanthanum and Actinium are d-block elements.

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    $\begingroup$ Couldn't it be a 15 in Lanthanide series and 15 in actinide series? Because chemical property is the period function of the atomic number. $\endgroup$ – Vishal Dec 16 '17 at 6:15

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