Periodic Table, The: Past, Present, And Future

room temperature [36]. It has also been proposed that cooled to its solid phase, oganesson would be a semiconductor [37].

And Beyond . . .

With the synthesis of element 117, the 7th Period has been completed. In Chapter 1, the issue of the future was addressed from the nucleosynthesis aspect. From the chemistry perspective, it is not about synthesizing a few fleeting atoms, but about finding long-lived isotopes — if they exist. Is there an “island of stability” yet to be found? If so, can super-neutron-rich projectiles be synthesized to bombard superheavy nuclei and reach the “island” [38]? Though such claims have been made before, it really does seem that the limit of actual chemistry of any new element has been reached. Yet there is the tantalization that such elements would open new possibilities in electron structure. Beyond the 8s orbitals loom the possibility of the 5g set. What are the properties of elements with g electrons? Will the orbitals fill in sequence or will things become “messy” as Pyykkö has suggested, in what is now called the Pyykkö Model [39].

Gilead has commented upon the “eka-elements” — those which are not actually known [40]:

There is no guarantee that they [eka-elements] will eventually be discovered, synthesized, or isolated as actual.

Perhaps this is indeed the completion of elemental chemistry as chemists know it.

Commentary

The actinoids exhibit a wider variety of chemical behavior than do the lanthanoids. Even though the first members of the actinoid series are no longer placed with the transition metals, nevertheless, in the highest oxidation states, there are strong chemical similarities to them. In addition, toward the end of the series, the preference for a 5f¹⁴ electron configuration marks results in two surprisingly low stable oxidation states. Unfortunately, the short half-lives of these later actinoids decrease the ability to fully explore their chemistry. Despite the strong influence of relativistic effects, even for the post-actinoid elements, the element properties so far seem to be mostly those expected for the appropriate group membership.

Will this continue into the 8th Period? As Haba has commented [41]:

Owing to the predicted strong influence of relativistic effect, any experimental investigation of their properties is fascinating.

Is attaining stable enough atoms of elements of the 8th Period a feasible goal or simply fantasy? Only time will tell.

References

1.P. J. Stewart, “Mendeleev’s Predictions: Success and Failure,” Found. Chem. 21, 3–9 (2019).

2.S. A. Cotton, Personal Communication, 06 October 2019.

3.H. J. Emeléus and J. S. Anderson, Modern Aspects of Inorganic Chemistry, Routledge & Sons Ltd., London, England (1938).

4.G. E. Villar, “On a Suggested Revision of the Seventh Period of the Periodic Table,” J. Chem. Educ. 19(6), 286 (1942).

5.G. E. Villar, “A Suggested Revision of the Position of Thorium in the Fourth Period of the Periodic Table,” J. Chem. Educ. 19(7), 329–330 (1942).

6.P. J. Stewart, “Charles Janet: Unrecognized Genius of the Periodic System,” Found. Chem. 12, 5–15 (2010).

7.G. T. Seaborg, “The Transuranium Elements,” Science 104, 379–386 (1946).

8.M. J. Laing, “The Question Mark at Uranium,” Found. Chem. 12, 27–30 (2010).

9.C. D. Coryell, “The Periodic Table: The 6d-5f Mixed Transition Group,” J. Chem. Educ. 29, 62–64 (1952).

10.N. Kaltsoyannis and A. Kerridge, “11: Chemical Bonding of Lanthanides and Actinides,” in G. Frenking and S. Shaik (Eds.), The Chemical Bond: Chemical Bonding Across the Periodic Table, Wiley-VCH, Weinheim, Germany, 342–343 (2014).

11.Yu. M. Kiselev et al., “On Existence and Properties of Plutonium (VIII) Derivatives,” Radiochim. Acta 102(3), 227–237 (2014).

12.W. Huang et al., “Is Octavalent Pu(VIII) Possible? Mapping the Plutonium Oxyfluoride Series PuO_nF_8–2n (n = 0–4),” Inorg. Chem. 54(17), 8825–8831 (2015).

13.R. J. Silva et al., “Comparative Solution Chemistry, Ionic Radius, and Single Ion Hydration Energy of Nobelium,” Inorg. Chem. 13(9), 2233–2237 (1974).

14.N. B. Mikheev, “Lower Oxidation States of Actinides,” Radiochim. Acta 32, 69–80 (1983).

15.A. Türler, “Lawrencium Bridges a Knowledge Gap,” Nature 520, 166–167 (2015).

16.K. Tatsumi and R. Hoffmann, “Bent cis d⁰ MoO₂²⁺ vs. Linear trans d⁰f⁰ UO₂²⁺: A Significant Role for Nonvalence 6p Orbitals in Uranyl,” Inorg. Chem. 19(9), 2656–2658 (1980).

17.D. C. Hoffman and D. M. Lee, “Chemistry of the Heaviest Elements — One Atom at a Time,” J. Chem. Educ. 76(3), 332–347 (1999).

18.H. E. Kremers, “Technology of the Rare Earths,” J. Chem. Educ. 62(8), 665–667 (1985).

19.W.-H. Xu and P. Pyykkö, “Is the Chemistry of Lawrencium Peculiar?” Phys. Chem. Chem. Phys. 18, 17351–17355 (2016).

20.S. G. Thompson, A. Ghiorso, and G. T. Seaborg, “The New Element Berkelium (Atomic Number 97),” Phys. Revs. 80, 781–789 (1950).

21.J. N. Cross et al., “Covalency in Americium(III) Hexachloride,” J. Am. Chem. Soc. 139, 8667–8677 (2017).

22.J. Maly et al., “Nobelium: Tracer Chemistry of the Divalent and Trivalent Ions,” Science 160, 1114–1115 (1968).

23.B. Kadkhodayan et al., “On-Line Gas Chromatographic Studies of Chlorides of Rutherfordium and Homologs Zr and Hf,” Radiochim. Acta 72(4), 169–178 (1996).

24.L. Öhrström, “Brief Encounters with Dubnium,” Nat. Chem. 8, 986 (2016).

25.M. Schädel et al., “Chemical Properties of Element 106 (Seaborgium),” Nature 388, 55–57 (1997).

26.J. Even et al., “Synthesis and Detection of a Seaborgium Carbonyl Complex,” Science 345(6203), 1491–1493 (2014).

27.R. Lougheed, “Oddly Ordinary Seaborgium,” Nature 388, 21–22 (1997).

28.R. Eichler et al., “Chemical Characterization of Bohrium (Element 107),” Nature 407, 63–65 (2000).

29.C. E. Düllman et al., “On the Stability and Volatility of Group 8 Tetroxides, MO₄ (M = Ruthenium, Osmium, and Hassium (Z = 108)),” J. Phys. Chem. B 106(26), 6679–6684 (2002).

30.D. Himmel et al., “How Far Can We Go? Quantum-Mechanical Investigations of Oxidation State +IX,” ChemPhysChem. 11(4), 865–869 (2010).

31.M. Patzschke and P. Pyykkö, “Darmstadtium Carbonyl and Carbide Resemble Platinum Carbonyl and Carbide,” Chem. Commun. 17, 1982–1983 (2004).

32.R. D. Hancock, L. J. Bartolotti, and N. Kaltsoyannis, “Density Functional Theory-Based Prediction of Some Aqueous-Phase Chemistry of Element 111. Roentgenium(I) Is the ‘Softest’ Metal Ion,” Inorg. Chem. 45(26), 10780–10785 (2006).

33.R. Eichler et al., “Thermochemical and Physical Properties of Element 112,” Angew. Chem. Int. Ed. Engl. 47(17), 3262–3266 (2008).

34.M. Seth and P. Schwerdtfeger, “The Chemistry of Superheavy Elements. III. Theoretical Studies on Element 113 Compounds,” J. Chem. Phys. 111, 6422–6433 (1999).

35.A. Yakushev et al., “Superheavy Element Flerovium (Element 114) Is a Volatile Metal,” Inorg. Chem. 53(3), 1624–1629 (2014).

36.R. M. MacRae and T. J. Kemp, “Oganesson: A Most