Editing Ruthenium (section)

==Characteristics==
===Physical properties===
[[File:Ruthenium crystals.jpg|thumb|left|Gas phase grown crystals of ruthenium metal]]

Ruthenium, a [[Valence (chemistry)#Common valences|polyvalent]] hard white metal, is a member of the [[platinum group]] and is in [[group 8 element|group&nbsp;8]] of the periodic table:

{| class="wikitable"
! [[Atomic number|Z]] !! [[Chemical element|Element]] !! [[Electron shell|No. of electrons/shell]]
|-
| 26 || [[iron]] || 2, 8, 14, 2
|-
| 44 || ruthenium || 2, 8, 18, 15, 1
|-
| 76 || [[osmium]] || 2, 8, 18, 32, 14, 2
|-
| 108 || [[hassium]] || 2, 8, 18, 32, 32, 14, 2
|}

Whereas all other group 8 elements have two electrons in the outermost shell, in ruthenium the outermost shell has only one electron (the final electron is in a lower shell). This anomaly is also observed in the neighboring metals [[niobium]]&nbsp;(41), [[molybdenum]]&nbsp;(42), and [[rhodium]]&nbsp;(45).

===Chemical properties===
Ruthenium has four crystal modifications and does not tarnish at ambient conditions; it oxidizes upon heating to {{convert|800|C|K}}. Ruthenium dissolves in fused alkalis to give ruthenates ({{chem|RuO|4|2-}}). It is not attacked by acids (even [[aqua regia]]) but is attacked by sodium hypochlorite at room temperature, and [[halogen]]s at high temperatures.{{sfnp|Haynes|2016|p=4.31}} Ruthenium is most readily attacked by oxidizing agents.{{sfnp|Greenwood|Earnshaw|1997|p=1076}} Small amounts of ruthenium can increase the hardness of [[platinum]] and [[palladium]]. The [[corrosion]] resistance of [[titanium]] is increased markedly by the addition of a small amount of ruthenium.{{sfnp|Haynes|2016|p=4.31}} The metal can be plated by [[electroplating]] and by thermal decomposition. A ruthenium–[[molybdenum]] alloy is known to be [[superconductivity|superconductive]] at temperatures below 10.6&nbsp;[[Kelvin|K]].{{sfnp|Haynes|2016|p=4.31}} Ruthenium is the only 4d&nbsp;transition metal that can assume the group oxidation state&nbsp;+8, and even then it is less stable there than the heavier congener osmium: this is the first group from the left of the table where the second and third-row transition metals display notable differences in chemical behavior. Like iron but unlike osmium, ruthenium can form aqueous cations in its lower oxidation +2 and +3&nbsp;states.{{sfnp|Greenwood|Earnshaw|1997|p=1078}}

Ruthenium is the first in a downward trend in the melting and boiling points and atomization enthalpy in the 4d&nbsp;transition metals after the maximum seen at [[molybdenum]], because the 4d&nbsp;subshell is more than half full and the electrons are contributing less to metallic bonding. ([[Technetium]], the previous element, has an exceptionally low value that is off the trend due to its half-filled [Kr]4d<sup>5</sup>5s<sup>2</sup> configuration, though it is not as far off the trend in the 4d series as [[manganese]] in the 3d&nbsp;transition series.){{sfnp|Greenwood|Earnshaw|1997|p=1075}} Unlike the lighter congener iron, ruthenium is usually [[paramagnetic]] at room temperature, as iron also is above its [[Curie point]].{{sfnp|Greenwood|Earnshaw|1997|p=1074}} However, the metastable tetragonal phase of ruthenium, created as a thin film on single crystal Mo, is ferromagnetic at room temperature.<ref>{{Cite journal |last1=Quarterman |first1=P. |last2=Sun |first2=Congli |last3=Garcia-Barriocanal |first3=Javier |last4=Dc |first4=Mahendra |last5=Lv |first5=Yang |last6=Manipatruni |first6=Sasikanth |last7=Nikonov |first7=Dmitri E. |last8=Young |first8=Ian A. |last9=Voyles |first9=Paul M. |last10=Wang |first10=Jian-Ping |date=2018-05-25 |title=Demonstration of Ru as the 4th ferromagnetic element at room temperature |journal=Nature Communications |language=en |volume=9 |issue=1 |pages=2058 |doi=10.1038/s41467-018-04512-1 |pmid=29802304 |issn=2041-1723|pmc=5970227 |bibcode=2018NatCo...9.2058Q }}</ref>

The reduction potentials in acidic aqueous solution for some common ruthenium species are shown below:{{sfnp|Greenwood|Earnshaw|1997|p=1077}}
{|class=wikitable
!Potential!!colspan=2|Reaction
|-
| 0.455 V ||Ru<sup>2+</sup> + 2e<sup>−</sup>|| ↔ Ru
|-
| 0.249 V ||Ru<sup>3+</sup> + e<sup>−</sup>|| ↔ Ru<sup>2+</sup>
|-
| 1.120 V ||RuO<sub>2</sub> + 4H<sup>+</sup> + 2e<sup>−</sup>|| ↔ Ru<sup>2+</sup> + 2H<sub>2</sub>O
|-
| 1.563 V ||{{chem|RuO|4|2-}} + 8H<sup>+</sup> + 4e<sup>−</sup>|| ↔ Ru<sup>2+</sup> + 4H<sub>2</sub>O
|-
| 1.368 V ||{{chem|RuO|4|-}} + 8H<sup>+</sup> + 5e<sup>−</sup>|| ↔ Ru<sup>2+</sup> + 4H<sub>2</sub>O
|-
| 1.387 V || RuO<sub>4</sub> + 4H<sup>+</sup> + 4e<sup>−</sup> || ↔ RuO<sub>2</sub> + 2H<sub>2</sub>O
|}

=== Isotopes ===
{{Main|Isotopes of ruthenium}}

Naturally occurring ruthenium is composed of seven stable [[isotope]]s. Additionally, 34 [[radioactive isotopes]] have been discovered. Of these [[radioisotope]]s, the most stable are <sup>106</sup>Ru with a [[half-life]] of 373.59&nbsp;days, <sup>103</sup>Ru with a half-life of 39.26&nbsp;days and <sup>97</sup>Ru with a half-life of 2.9 days.<ref name="n1" /><ref name="n2" />

Fifteen other radioisotopes have been characterized with [[atomic weight]]s ranging from {{val|89.93|ul=Da}} (<sup>90</sup>Ru) to 114.928&nbsp;Da (<sup>115</sup>Ru). Most of these have half-lives that are less than five minutes; the exceptions are <sup>95</sup>Ru (half-life 1.643&nbsp;hours) and <sup>105</sup>Ru (half-life 4.44&nbsp;hours).<ref name="n1" /><ref name="n2" />

The primary [[decay mode]] before the most abundant isotope, <sup>102</sup>Ru, is [[electron capture]] while the primary mode after is [[beta emission]]. The primary [[decay product]] before <sup>102</sup>Ru is [[technetium]] and the primary decay product after is [[rhodium]].<ref name="n1">{{RubberBible86th}} Section&nbsp;11, Table of the Isotopes</ref><ref name="n2">{{NUBASE 2003}}</ref>

<sup>106</sup>Ru is a product of fission of a nucleus of [[uranium]] or [[plutonium]]. High concentrations of detected atmospheric <sup>106</sup>Ru were associated with an alleged [[Airborne radioactivity increase in Europe in autumn 2017|undeclared nuclear accident in Russia]] in 2017.<ref name="pnas2019">
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</ref>

=== Occurrence ===
{{See also|Category:Ruthenium minerals}}
Ruthenium is found in about 100&nbsp;[[parts per trillion]] in the Earth's crust, making it the [[Abundance of the chemical elements|78th most abundant element]].{{sfnp|Greenwood|Earnshaw|1997|p=1071}} It is generally found in ores with the other platinum group metals in the [[Ural Mountains]] and in North and South America. Small but commercially important quantities are also found in [[pentlandite]] extracted from [[Greater Sudbury|Sudbury]], [[Ontario]], Canada, and in [[pyroxenite]] deposits in [[South Africa]]. The native form of ruthenium is a very rare mineral (Ir replaces part of Ru in its structure).<ref name="USGS-YB-2006">{{cite web |url = http://minerals.usgs.gov/minerals/pubs/commodity/platinum/myb1-2006-plati.pdf |publisher = United States Geological Survey USGS |access-date = 2008-09-16 |title = 2006 Minerals Yearbook: Platinum-Group Metals |first = Micheal W. |last = George |archive-date = 11 January 2019 |archive-url = https://web.archive.org/web/20190111062032/https://minerals.usgs.gov/minerals/pubs/commodity/platinum/myb1-2006-plati.pdf |url-status = dead }}</ref><ref name="USGS-CS-2008">{{cite web |url = http://minerals.usgs.gov/minerals/pubs/commodity/platinum/mcs-2008-plati.pdf |publisher = United States Geological Survey USGS |access-date = 2008-09-16 |title = Commodity Report: Platinum-Group Metals |archive-date = 11 January 2019 |archive-url = https://web.archive.org/web/20190111015125/https://minerals.usgs.gov/minerals/pubs/commodity/platinum/mcs-2008-plati.pdf |url-status = dead }}</ref> Ruthenium has a relatively high [[fission product yield]] in nuclear fission; and given that its most long-lived radioisotope has a half life of "only" around a year, there are often proposals to recover ruthenium in a new kind of [[nuclear reprocessing]] from [[spent fuel]]. An unusual ruthenium deposit can also be found at the [[natural nuclear fission reactor]] that was active in [[Oklo]], Gabon, some two billion years ago. Indeed, the isotope ratio of ruthenium found there was one of several ways used to confirm that a nuclear fission chain reaction had indeed occurred at that site in the geological past. Uranium is no longer mined at Oklo, and there have never been serious attempts to recover any of the platinum group metals present there.