Sciencemadness Discussion Board

Variations in Periodic Table Layout

j_sum1 - 30-4-2015 at 18:17

A question that I have wondered over for some time and eventually put into the "doesn't matter" category. But maybe it is relevant...

What is the correct or most logical positioning of the f block elements in a periodic table. Specifically, are Scandium and Yttrium better associated with Lanthanum and Actinium or with Lutetium and Lawrencium? Or maybe with neither? Often the f block is shown as 15 elements wide but occasionally 14. Consider these examples:

f block is 14 wide, Lu below Y
Standard presentation
wide table

f block is 15 wide
standard presentation This seems to be the most common configuration but is of course ambiguous.
wide version

f block is 14 wide with La below Y
standard presentation
wide version

hedging your bets by duplicating elements
http://www.av8n.com/physics/img48/pt-full.png



By way of adding something to the discussion and not just asking the question, I take the situation as being analogous to the d block. In my understanding, the zinc group is not properly considered a transition metal since it does not have partly filled d subshell. However it is still considered part of the d block when it comes to organising the elements.

Are there precise and distinct definitions for the terms "Rare Earth", "Lanthanide", "Actinide" "f block element"? I am sure that there are. Where do the edge elements La, Ac, Lu and Lw fit under these definitions? Which is the most appropriate categorisation to make when it comes to organising the elements?
Or are we well into the realm of splitting hairs when a functional approach is most desirable: considering each element's properties and behaviour individually and only grouping them in ways that suit our own particular practical purpose?

blogfast25 - 1-5-2015 at 07:46

Quote: Originally posted by j_sum1  
By way of adding something to the discussion and not just asking the question, I take the situation as being analogous to the d block. In my understanding, the zinc group is not properly considered a transition metal since it does not have partly filled d subshell. However it is still considered part of the d block when it comes to organising the elements.

Or are we well into the realm of splitting hairs when a functional approach is most desirable: considering each element's properties and behaviour individually and only grouping them in ways that suit our own particular practical purpose?


In a nutshell, it's splitting hairs. Where else would one put Zn, for instance? So the d subshell is filled, so what? Would one use the same argument on Ca? That its s shell is filled? It's nonsense.

Same with La, Ac. La behaves very much like an RE, thank you very much!

Lanthanum’s [Xe] 5d<sup>1</sup> 6s<sup>2</sup> electron configuration is really an anomaly of Madelung’s Rule: http://en.wikipedia.org/wiki/Atomic_orbital#Electron_placeme...

So, it ‘should’ have been [Xe] 4f<sup>1</sup> 6s<sup>2</sup> but due to the energy vicinity of 4f and 5d there’s an inversion.

The case for Lu not being an f block element is much stronger.



In the case of Ac, only from about Cm do the actinides really start behaving like f-block elements: the lower ones have oxidation states that are all over the place, without much of a pattern really.

Note that using the wide presentations, your Tc, Pm, Np spiel goes out of the window. ;)

'brain&force' presented another, very different kind of PT presentation somewhere on this forum but I can't find it right now.

Edit: ooopsie, found it:

http://en.wikipedia.org/wiki/Alternative_periodic_tables#Lef...

So if you want to 'think outside the box', try that one! ;)


[Edited on 1-5-2015 by blogfast25]