What is traditional Periodic Table based upon?

[Vts]

Someone asked me recently: What is the basic principle behind the layout of the traditional Periodic Table?

I can not answer this question in one short sentence. Can you?

[hermanntrude]

Basically you take the elements and line them up in order of atomic mass, and then take any point where a set of physical properties has a reccuring value (maximum or minimum) and put it underneath the previous value so that the element's properties recur periodically.

[Vts]

Would it be correct to say then that traditional PT is constructed on the basis of physical properties of elements?

 

Dmitri Mendeleev has warned that properties of the elements should not be a basis for the Periodic Table since they may vary a great deal under the influence of the environmental conditions, such as temperature and pressure. Helium supposedly acts as a metal in the cores of large planets, such as jupiter, etc. Therefore, our Periodic table would take a different form, if we would live on a different planet.

[UC]

Well, if you want to get technical, it follows the number of protons in the nuclei (and hence order of filling of the ellectrons) and the quantum states that the electrons are in: aka: shells and subshells.

[hermanntrude]

UC, it's not really as simple as that. For instance, the f-block elements nearly all have exceptions to the electronic configuration you'd expect based on their positions in the periodic table. The similarities in physical properties of adjacent elements is much more coherent

[UC]

I realize this. It does get rather sketchy in places, but you can't argue atomic number or the s, p, d, and f blocks as a general means of organization. The properties of the elements arise at least partly, if not mostly from their electron configurations, and as a result, are just as inconsistent in places as the electron configurations.

[hermanntrude]

if you want a periodic table which is arranged in accordance with electronic configuration, then you can't do better than the ADOMAH periodic table:

 

http://perfectperiodictable.com/

[mabsj2]

its based upon their Atomic Number (number of protons). since the number of unpaired electrons determines the chemical properties of the elements. its logical that elements in the same group will have the same properties

[hermanntrude]

mabsj2:

 

if the PT was simply based on atomic number it'd be a line of elements 120 elements long. What do you think the basis for ending a row is?

[Vts]

its based upon their Atomic Number (number of protons). since the number of unpaired electrons determines the chemical properties of the elements. its logical that elements in the same group will have the same properties

 

Well, it is true only to a certain extent. As reported recently in Science News, group of scientists in Switzerland have determined that element 114 acts more like a noble gas, not as Pb. There are other mysterious relationships, such as Knight move, for example. Therefore, if we look simply at the properties, we could break up the sequence in many different ways. I think that the only correct way is to sort elements by spdf blocks. And, since it is the most logical way, the blocks should be placed in correct order, that is spdf, in accordance with the quantum number "l=0,1,2,3...", no sfdp (l=0,3,2,1) order, as in traditional table.

Edited January 12, 2009 by Vts

[Vts]

It does get rather sketchy in places, but you can't argue atomic number or the s, p, d, and f blocks as a general means of organization.

 

Well, La for example does not even have f-electron. How can we put it in f-block? I think, I found good answer to that question that has two parts:

 

First, we make sure that continuity of atomic numbers Z is preserved, that is (56)Ba precedes (57)La that is followed by (58)Ce, etc;

 

Second, we break the sequence of the elements in accordance with value of (n+l) of newly added electron: for Ba n+l=6, for La n+l=7, so is for Ce n+l=7. The break should be between Ba and La, where "n+l" changes to a higher value. Not between La and Ce, as was shown in older periodic tables. Therefore, 7th period naturally starts with La, despite the absence of f-electron.

 

One might ask why was "n+l" rule chosen for braking the sequence of the elements in periods? Well, because it was empirically determined that electrons generally follow "n+l" order when they take their places around the nucleus (and also vacate their places during ionization). So, it is quite logical to suggest that new period should start with the element that has newly added electron reaching new high "n+l" value.

 

That what makes Janet's LSPT and its recent offspring ADOMAH PT objectively unique.

Edited January 15, 2009 by Vts

[UC]

The feeling I'm getting is that you started this thread with the sole purpose of rambling about that link in your sig. that was already there when you started the thread. I don't particularly appreciate this.

[hermanntrude]

you'll have to forgive Vts. He's come up with a new form of PT and he wants the world to know about it BADLY. If you check out the table you'll see why. While the targetted posting is against usual nettiquette, I figure I'd probably do it too if it was my PT.

[Vts]

Thanks for support, Hermanntrude. I should have also included link to the Janet's LSPT.

 

The feeling I'm getting is that you started this thread with the sole purpose of rambling about that link in your sig. that was already there when you started the thread. I don't particularly appreciate this.

 

I belong to a group of people who believe that the Periodic Table should be based on Electron Configurations. That is why I started this thread.

I'm completing it by asking to forgive my obsession.

Edited January 15, 2009 by Vts