mardi 23 septembre 2008
Periodic table of the chemical elements quantum mechanics consistent
The usual periodic tables of the chemical elements are already 97 % in accord with quantum mechanics. Three elements only do not fit correctly into it, in disagreement with the Pauli exclusion principle[1]. In order to ensure coherence, it is put forward to place helium beside hydrogen into the s-block. Lutetium and lawrencium pertain to the d-block of the transition metals and should not be in the f block with the rare earths or the actinoids. By replacing the lanthanoids (rare earths or lanthanides) and actinoids (actinides) boxes of the official IUPAC periodic table by those of lutetium and lawrencium, with helium placed beside hydrogen, the compact periodic table is 100 % quantum mechanics correct.
History of the periodic table
The Mendeleev table is more than one century old. The number of columns was
6 in 1869, corrected to 8 in 1871, at the origin, based on atomic
masses with twelve lines and eight columns, corresponding approximately
to the s, p and d-blocks of quantum mechanics. The transition metals
were moved separately and the corresponding column was replaced by the
rare gases after their discovery by Ramsay. Moseley replaced the mass
with the atomic number as a classification criterion. The transuranians
were discovered by Seaborg who placed the lanthanoids and actinoids
separately, below the table, for reasons of compactness.
Various table shapes may be found in the literature. On the usual ones, one
line is a period with a total of 6 periods. Columns are grouped
approximately in four blocks named s, p, d, f, respectively for the
values 0, 1, 2, 3 of the second quantum number l. Each block contains
theoretically an even number of elements (a consequence of the Pauli
exclusion principle). They are given by the formula 2(2l + 1) e.g. 2,
6, 10, 14. On the IUPAC official table[2], shown on figure 1 there are
18 columns. Columns 3 to 12 form the d group, the transition metals,
formerly part of Mendeleev group VIII. Column VIII was then used for
the rare gases and renamed 18. The f block (l = 3) is apart.
Although updated many times, the periodic table has some anomalies shown on
figure 1 with question marks. There is a vacant box beside hydrogen and
a strange discontinuity below yttrium. With the advent of quantum
mechanics, the periodic table got a theoretical background that solves
these anomalies (in grey on figure 1 below).
Helium
It is well known that helium has a 1s2 structure, with two electrons,
which is a spherical mode of vibration, the same as hydrogen 1s1, with
one electron. Helium, pertaining to the s block, is usually placed with
the other rare gases in the p block[3] where the electronic structure is
np6 with six electrons in the outer shells instead of two for helium.
In 1962 Bartlett[4] showed that the noble gases were not so inert. There
exists compounds of xenon and krypton with fluor, chlorine, hydrogen,
platinum[4], gold[5] … There is no chemical reason any more to place
helium with the other noble gases6. The vacant box beside hydrogen
should filled with helium where it has its natural place, in accord
with quantum mechanics as put forward by Bohr in 1921[1].
Lutetium and lawrencium
Lutetium and lawrencium are traditionally considered as belonging respectively
to lanthanoids and actinoids having 15 elements each. According to the
Pauli exclusion principle, the f block contains an even maximum of 14
electrons. Lutetium (also named Cassiopium Cp) pertains to the d block
of the transition metals1 with 10 elements and therefore not to the
f-block of the lanthanoids. Lutetium is not included in the study of
the valency of rare earths by Strange et al[7]. According to Jensen[8],
physical and chemical properties unanimously favour the placement of
lutetium below scandium and yttrium and not within the lanthanoids.
This is also valid for the actinoids, mostly unknown at the time of
Bohr. A physical or chemical classification criterion seems difficult
to apply to the newly discovered actinoids that decay seconds after
they are formed[9].
Suggested updating of the periodic table (Figure 2 above)
Bent[6] recommends to place helium above beryllium. The exclusion principle is
therefore satisfied. Lutetium and lawrencium should be in the d-block
below scandium and yttrium. The lanthanoids and actinoids are now 14
each as predicted by quantum mechanics for the f block. The only
unambiguous classification criterion is the electronic structure, as
was put forward by Bohr and Pauli more than seventy years ago[1]. The
drawings show the nodes of the vibration modes of the outer shells of
the atoms [10].
References
1. Born M., Dougall J., Radcliffe J.M., Blin-Stoyle, R.J., Atomic Physics. Dover, New York, 1989 (first édition in 1935).
2. Holden, N.E. and Coplen Ty., The Periodic Table of the Elements. Chemistry International, 26, No. 1 January-February 2004
3. Scerri, E.R., Some aspects of the metaphysics of chemistry and the nature of the elements. HYLE. 11 (1-2), pp. 127-145, 2005.
4. Bartlett N., Xenon Hexafluoroplatinate(V) Xe+[PtF6]–. Proc. Chem. Soc. (June), 218, 1962.
5. Brisdon A.K., Halogens and Noble Gases. Annu. Rep. Prog. Chem., Sect. A, 97, 107–116, 2001.
6. Bent, A., New Ideas in Chemistry from Fresh Energy for the Periodic Law. Authorhouse, Bloomington, IN, 2006
7. Strange, P., Svane, A., Temmerman, W. M., Szotek, Z., Winter H.,
Understanding the valency of rare earths from first-principles theory.
Nature (London), 399, 756-758, 1999.
8. Jensen, W.B., The Positions of Lanthanum (Actinium) and Lutetium (Lawrencium) in the Periodic
Table. Journal of Chemical Education, 59, p. 634-636, 1982.
9. Kendall Powell, Heavy elements: A very brief encounter. Nature, 418, 815-816, 2002.
10. Schaeffer, B., Relativités et quanta clarifiés, Publibook, Paris, 2007