Vts

"Why would La be counted in f when when the config. is 5d 6s ...!" Now I know why. The periodic's law basic rule is "n+l" rule. That is, periodicity follows "n+l", and not "n" or "l" separately. Value of "n+l" for determining electron in La is 7 (either 4f or 5d orbitals), so as for Lanthanides. If you want to see how it works, go to perfectperiodictable.com. It is demonstrated there clearly.

In old periodic tables La was listed in 5d subshell, that corresponds to n=5 and l=2 quantum numbers. Modern IUPAC table lists it in 4f subshell, that corresponds to n=4, l=3. It is known that La has no 4f electron, but it did not stop IUPAC from listing it in 4f. What is correct eigenvalue of the last distinct electron to be used for the solving Schrodinger equation for example? Should n=4 and l=3 be used? I

If you list the elements by the atomic numbers or weights only it would be single continuous line or column of the elements. We know now that periodicity is based on n+l rule, aufbau principle, Hund's rule and Pauli Exclusion principle. All of the above, as well as chemical and physical properties, ultimately connected to the electronic configurations, which are described by the quantum numbers n, l, ml and ms. Why not the Periodic Table? If Periodic Table is based strictly on the quantum numbers, perhaps some mysterious chemical relationships could be solved.

Do you mean atomic weights? I do not think that he even knew about the atomic numbers at that time. He used what he had. But if he had known about the quantum numbers, which are certainly the "exact numbers", wouldn't he come up with a formulation that reflects them in some way? I bet he would look into that.

The spdf blocks ( that reflect only quantum number l) are visible in the IUPAC Periodic Table and principal quantum number n is followed only for the first three periods, but traditional Periodic Table is not built in order of the quantum numbers. Even spdf blocks are not in the correct order. Left Step PT is built in order of quantum numbers l and in accordance with n+l rule. ADOMAH PT is the only periodic table that is ordered in accordance with all four quantum numbers. It naturally folds into the regular tetrahedron, which is quite remarkable.

I was surprised to read in Dmitri Mendeleev's 'The Relations between the Properties of Elements and Their Atomic Weights': '...every (periodic) system, however, that is based upon exactly observed numbers is to be preferred of course to other systems not based upon numbers because then only little margin is left to arbitrariness... Properties, such as the optical and even the electrical or magnetic ones, cannot serve as basis for the system naturally, since one and the same body, according to the state in which it happens to be at the moment, may show enormous differences in this regard.' Wait a minute, today's standard IUPAC Periodic Table does not follow that rule in regard to the quantum numbers, which are the most exact numbers by definition. Traditional Periodic Table, by separating metals from non metals, completely ignores quantum numbers n, l, ml and ms, which define electronic configurations of the atoms, which, in turn, define the nature of the elements. What if we bring the traditional Periodic Table in conformance with the quantum numbers as in ADOMAH Periodic Table http://www.meta-synthesis.com/webbook/35_pt/pt.html#perfect ? Blocks of the Periodic Table (fdps) become equally spaced slices of the regular tetrahedron! Bravo, Dmitri Mendeleev!

I am new here and I have following question: I read the rules when I registered and it is still not clear to me if it is allowed to mention websites while posting messages which deal only with scientific questions and have no stuff to sell, etc. I tried to contact the administrator, but did not receive a reply.

Hi there: I love discussions about the Periodic Table the History of Science in general and Chemistry in particular. I hope to find to make friends here, so I can chat about those subjects. I'll see you !