Editing Period 5 element (section)

==Physical properties==

This period contains [[technetium]], one of the two elements until [[lead]] that has no stable isotopes (along with [[promethium]]), as well as [[molybdenum]] and [[iodine]], two of the heaviest elements with a known biological role.<ref>{{cite web|url=http://www.3rd1000.com/elements/Iodine.htm |title=Iodine |publisher=3rd1000.com |access-date=2012-08-13}}</ref><ref>{{cite web|url=http://www.webelements.com/molybdenum/biology.html |title=WebElements Periodic Table of the Elements &#124; Molybdenum &#124; biological information |publisher=Webelements.com |access-date=2012-08-13}}</ref> [[Niobium]] has the largest known magnetic penetration depth of all the elements.<ref>{{cite journal|title = A Superconducting Nb<sub>3</sub>Sn Coated Multicell Accelerating Cavity|first = M.|last = Peiniger|author2=Piel, H. |journal = IEEE Transactions on Nuclear Science|date= 1985|volume= 32|issue = 5|doi = 10.1109/TNS.1985.4334443|pages = 3610–3612|bibcode = 1985ITNS...32.3610P |s2cid = 23988671}}</ref> [[Zirconium]] is one of the main components of [[zircon crystals]], currently the oldest known minerals in the Earth's crust. Many later [[transition metals]], such as rhodium, are very commonly used in jewelry as they are very shiny.<ref name="Gray" >{{cite book|last=Gray|first=Theodore|title=The Elements: A Visual Exploration of Every Known Atom in the Universe|year=2009|publisher=Black Dog & Leventhal Publishers|location=New York|isbn=978-1-57912-814-2|url-access=registration|url=https://archive.org/details/elementsvisualex0000gray}}</ref>

This period is known to have a large number of exceptions to the [[Madelung rule]].