Editing Gadolinium (section)

===Physical properties===
Gadolinium is the eighth member of the [[lanthanide]] series. In the [[periodic table]], it appears between the elements [[europium]] to its left and [[terbium]] to its right, and above the [[actinide]] [[curium]]. It is a silvery-white, [[malleability|malleable]], [[ductility|ductile]] [[rare-earth element]]. Its 64 electrons are arranged in the configuration of [Xe]4f<sup>7</sup>5d<sup>1</sup>6s<sup>2</sup>, of which the ten 4f, 5d, and 6s electrons are [[valence electron|valence]].

Like most other metals in the lanthanide series, three electrons are usually available as valence electrons. The remaining 4f electrons are too strongly bound: this is because the 4f orbitals penetrate the most through the inert xenon core of electrons to the nucleus, followed by 5d and 6s, and this increases with higher ionic charge. Gadolinium crystallizes in the [[hexagonal crystal system|hexagonal close-packed]] α-form at room temperature.   At temperatures above {{convert|1235|C}}, it forms or transforms into its β-form, which has a [[body-centered cubic]] structure.<ref name="Greenwood" />

The [[isotope]] gadolinium-157 has the highest [[thermal neutron|thermal-neutron]] [[neutron capture|capture]] cross-section among any stable nuclide: about 259,000 [[barn (unit)|barns]]. Only [[xenon-135]] has a higher capture cross-section, about 2.0&nbsp;million barns, but this isotope is [[radioactive]].<ref name="barn">{{cite journal |url= https://www.ncnr.nist.gov/resources/n-lengths/elements/gd.html |title= Gadolinium |access-date= 6 June 2009 |journal= Neutron News |volume= 3 |issue= 3 |date= 1992 |page= 29}}</ref>

Gadolinium is believed to be [[ferromagnetism|ferromagnetic]] at temperatures below {{convert|20|C}}<ref name="CRC2" /> and is strongly [[paramagnetism|paramagnetic]] above this temperature. In fact, at body temperature, gadolinium exhibits the greatest paramagnetic effect of any element.<ref name="Wininger">{{cite journal |last1=Wininger |first1=Kevin |title=Contrast Media's Molecular Architecture |journal=Radiologic Technology |date=January–February 2022 |volume=93 |issue=3 |page=341 |pmid=35017275 |url=https://cdn.mycrowdwisdom.com/asrt/CE%20Column/RADT22_JF_MolArch.pdf |access-date=27 November 2023}}</ref> There is evidence that gadolinium is a helical antiferromagnetic, rather than a ferromagnetic, below {{convert|20|C}}.<ref name="CoeySkumryev1999">{{cite journal |vauthors= Coey JM, Skumryev V, Gallagher K |journal=Nature |volume=401 |issue=6748 |year=1999 |pages=35–36|issn=0028-0836|doi=10.1038/43363 |title= Rare-earth metals: Is gadolinium really ferromagnetic?|bibcode=1999Natur.401...35C|s2cid=4383791 }}</ref> Gadolinium demonstrates a [[magnetic refrigeration#The magnetocaloric effect|magnetocaloric effect]] whereby its temperature increases when it enters a magnetic field and decreases when it leaves the magnetic field. A significant magnetocaloric effect is observed at higher temperatures, up to about 300&nbsp;[[kelvin]]s, in the compounds Gd<sub>5</sub>(Si<sub>1−''x''</sub>Ge<sub>''x''</sub>)<sub>4</sub>.<ref name="r27" />

Individual gadolinium atoms can be isolated by encapsulating them into [[fullerene]] molecules, where they can be visualized with a [[transmission electron microscope]].<ref>{{cite journal |doi= 10.1021/nl034621c |title= Evidence for the Intramolecular Motion of Gd Atoms in a Gd<sub>2</sub>@C<sub>92</sub> Nanopeapod |date= 2003 |author= Suenaga, Kazu |journal= Nano Letters |volume= 3 |pages= 1395 |first2= Risa |first3= Takashi |first4= Toshiya |first5= Hisanori |first6= Sumio |last2= Taniguchi |last3= Shimada |last4= Okazaki |last5= Shinohara |last6= Iijima|bibcode= 2003NanoL...3.1395S |issue= 10}}</ref> Individual Gd atoms and small Gd clusters can be incorporated into [[carbon nanotubes]].<ref>{{cite journal |vauthors= Hashimoto A, Yorimitsu H, Ajima K, Suenaga K, Isobe H, Miyawaki J, Yudasaka M, Iijima S, Nakamura E |title= Selective deposition of a gadolinium(III) cluster in a hole opening of single-wall carbon nanohorn |journal= Proceedings of the National Academy of Sciences, USA |volume= 101 |issue= 23 |pages= 8527–30 |date= June 2004 |pmid= 15163794 |pmc= 423227 |doi= 10.1073/pnas.0400596101 |bibcode= 2004PNAS..101.8527H|doi-access= free }}</ref>