Editing Technetium (section)

===Physical properties===
Technetium is a silvery-gray radioactive [[metal]] with an appearance similar to [[platinum]], commonly obtained as a gray powder.{{sfn|Hammond|2004|p={{page needed|date=June 2021}}}} The [[crystal structure]] of the bulk pure metal is [[Hexagonal crystal system|hexagonal]] [[close-packed]]. Atomic technetium has characteristic [[Emission spectrum|emission lines]] at [[wavelength]]s of 363.3&nbsp;[[Nanometre|nm]], 403.1&nbsp;nm, 426.2&nbsp;nm, 429.7&nbsp;nm, and 485.3&nbsp;nm.<ref>{{cite book | first=David R. | last=Lide |date = 2004–2005 |chapter = Line spectra of the elements |title = The CRC Handbook |publisher =CRC press |pages=10–70 (1672) | isbn=978-0-8493-0595-5 |chapter-url=https://books.google.com/books?id=q2qJId5TKOkC&pg=PT1672 }}</ref> The unit cell parameters of the orthorhombic Tc metal were reported when Tc is contaminated with carbon ({{mvar|a}} = 0.2805(4), {{mvar|b}} = 0.4958(8), {{mvar|c}} = 0.4474(5)·nm for Tc-C with 1.38 wt% C and {{mvar|a}} = 0.2815(4), {{mvar|b}} = 0.4963(8), {{mvar|c}} = 0.4482(5)·nm for Tc-C with 1.96 wt% C ).<ref name="carbide"/> The metal form is slightly [[paramagnetism|paramagnetic]], meaning its [[dipole|magnetic dipoles]] align with external [[magnetic field]]s, but will assume random orientations once the field is removed.<ref name=enc>{{cite book |last=Rimshaw |first=S.J. |date=1968 |editor-last=Hampel |editor-first=C.A. |title=The Encyclopedia of the Chemical Elements |location=New York, NY |publisher=Reinhold Book Corporation |url=https://archive.org/details/encyclopediaofch00hamp |url-access=registration |pages=[https://archive.org/details/encyclopediaofch00hamp/page/689 689–693] }}</ref> Pure, metallic, single-crystal technetium becomes a [[type-II superconductor]] at temperatures below {{convert|7.46|K|abbr=on|lk=in}}.{{sfn|Schwochau|2000|p=96}}{{efn|
Irregular crystals and trace impurities raise this transition temperature to 11.2&nbsp;K for 99.9% pure technetium powder.{{sfn|Schwochau|2000|p=96}}
}}
Below this temperature, technetium has a very high [[London penetration depth|magnetic penetration depth]], greater than any other element except [[niobium]].<ref>{{cite conference |last = Autler |first=S.H. |date=Summer 1968 |title = Technetium as a material for AC superconductivity applications |conference = 1968 Summer Study on Superconducting Devices and Accelerators |url = http://www.bnl.gov/magnets/Staff/Gupta/Summer1968/0049.pdf |access-date = 2009-05-05}}</ref>