Actinide: Difference between revisions

{{short description|F-block chemical elements}}

{{Use dmy dates|date=May 2020}}

{{Sidebar periodic table|expanded=metalicity}}

The 1985 [[IUPAC nomenclature of inorganic chemistry|IUPAC ''Red Book'']] recommends that ''actinoid'' be used rather than ''actinide'', since the suffix ''-ide'' normally indicates a [[negative ion]]. However, owing to widespread current use, ''actinide'' is still allowed.

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The existence of transuranium elements was suggested in 1934 by [[Enrico Fermi]], based on his experiments.<ref>{{cite journal|title=Possible Production of Elements of Atomic Number Higher than 92|journal=Nature|author= E. Fermi|bibcode=1934Natur.133..898F|year=1934|volume=133|pages=898–899|doi=10.1038/133898a0|issue=3372|doi-access=free}}</ref><ref>{{cite book|first1=Jagdish |last1=Mehra |first2=Helmut |last2=Rechenberg |author-link1=Jagdish Mehra|author-link2=Helmut Rechenberg|title=The historical development of quantum theory|url=https://books.google.com/books?id=kn6mb0ltm0UC&pg=PA966|year=2001|publisher=Springer|isbn=978-0-387-95086-0|page=966}}</ref> However, even though four actinides were known by that time, it was not yet understood that they formed a family similar to lanthanides. The prevailing view that dominated early research into transuranics was that they were regular elements in the 7th period, with thorium, protactinium and uranium corresponding to 6th-period [[hafnium]], [[tantalum]] and [[tungsten]], respectively. Synthesis of transuranics gradually undermined this point of view. By 1944, an observation that curium failed to exhibit oxidation states above 4 (whereas its supposed 6th period homolog, [[platinum]], can reach oxidation state of 6) prompted [[Glenn Seaborg]] to formulate an "[[actinide concept|actinide hypothesis]]". Studies of known actinides and discoveries of further transuranic elements provided more data in support of this position, but the phrase "actinide hypothesis" (the implication being that a "hypothesis" is something that has not been decisively proven) remained in active use by scientists through the late 1950s.<ref>{{cite book|title=Handbook on the Physics and Chemistry of Rare Earths|volume=18 – Lanthanides/Actinides: Chemistry|editor1=K.A. Gschneidner Jr., L|editor2=Eyring, G.R. Choppin|editor3=G.H. Landet|year=1994|publisher=Elsevier|chapter=118 – Origin of the actinide concept|author=Seaborg, G. T.|pages=4–6, 10–14}}</ref><ref>{{cite journal|doi=10.1021/ed036p340|title=The first isolations of the transuranium elements: A historical survey|year=1959|last1=Wallmann|first1=J. C.|journal=Journal of Chemical Education|volume=36|issue=7|page=340|bibcode = 1959JChEd..36..340W |url=http://www.escholarship.org/uc/item/7jx8p5z6}}</ref>

: <math chem>\ce{{^{238}_{92}U} + {}^{1}_{0}n -> {}^{239}_{92}U ->[\beta^-] [23.5\ \ce{min}] {}^{239}_{93}Np ->[\beta^-] [2.3\ \ce{days}] {}^{239}_{94}Pu} \left( \ce{->[\alpha] [2.4\cdot 10^4\ \ce{years}]} \right) \ce{{^{235}_{92}U}}</math>

Actinides with the highest mass numbers are synthesized by bombarding uranium, plutonium, curium and californium with [[ion]]s of nitrogen, oxygen, carbon, neon or boron in a [[particle accelerator]]. Thus [[nobelium]] was produced by bombarding uranium-238 with [[neon-22]] as

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The abundance of actinium in the Earth's crust is only about 5{{e|-15}}%.<ref name="Himiya protaktiniya" /> Actinium is mostly present in uranium-containing, but also in other minerals, though in much smaller quantities. The content of actinium in most natural objects corresponds to the isotopic equilibrium of parent isotope ²³⁵U, and it is not affected by the weak Ac migration.<ref name="Himiya aktiniya" /> Protactinium is more abundant (10⁻¹²%) in the Earth's crust than actinium. It was discovered in uranium ore in 1913 by Fajans and Göhring.<ref name=fajans /> As actinium, the distribution of protactinium follows that of ²³⁵U.<ref name="Himiya protaktiniya" />

== Properties ==

The shift of electron configurations in the gas phase does not always match the chemical behaviour. For example, the early-transition-metal-like prominence of the highest oxidation state, corresponding to removal of all valence electrons, extends up to uranium even though the 5f shells begin filling before that. On the other hand, electron configurations resembling the lanthanide congeners already begin at plutonium, even though lanthanide-like behaviour does not become dominant until the second half of the series begins at curium. The elements between uranium and curium form a transition between these two kinds of behaviour, where higher oxidation states continue to exist, but lose stability with respect to the +3 state.<ref name=johnson/> The +2 state becomes more important near the end of the series, and is the most stable oxidation state for nobelium, the last 5f element.<ref name=johnson/> Oxidation states rise again only after nobelium, showing that a new series of 6d transition metals has begun: [[lawrencium]] shows only the +3 oxidation state, and [[rutherfordium]] only the +4 state, making them respectively congeners of lutetium and hafnium in the 5d row.<ref name=johnson/>

!Core charge {{nobold|1=(''Z'')}}

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!Atomic mass