Editing Technetium (section)

==Isotopes==
{{main|Isotopes of technetium}}
Technetium, with [[atomic number]] ''Z''&nbsp;= 43, is the lowest-numbered element in the periodic table for which all isotopes are [[radioactive]]. The second-lightest exclusively radioactive element, [[promethium]], has atomic number 61.<ref name=LANL/> [[Atomic nucleus|Atomic nuclei]] with an odd number of [[proton]]s are less stable than those with even numbers, even when the total number of [[nucleon]]s (protons + [[neutron]]s) is even,<ref>{{cite book |last=Clayton |first=D.D. |date=1983 |title=Principles of stellar evolution and nucleosynthesis: with a new preface |publisher=University of Chicago Press |isbn=978-0-226-10953-4 |url=https://archive.org/details/principlesofstel0000clay |url-access=registration |page=[https://archive.org/details/principlesofstel0000clay/page/547 547] }}</ref> and odd numbered elements have fewer stable [[isotope]]s.

The most stable [[Radionuclide|radioactive isotopes]] are technetium-97 with a [[half-life]] of {{val|4.21|0.16}}&nbsp;million&nbsp;years and technetium-98 with {{val|4.2|0.3}}&nbsp;million&nbsp;years; current measurements of their half-lives give overlapping [[confidence interval]]s corresponding to one [[standard deviation]] and therefore do not allow a definite assignment of technetium's most stable isotope. The next most stable isotope is technetium-99, which has a half-life of 211,100&nbsp;years.{{NUBASE2020|ref}} Thirty-four other radioisotopes have been characterized with [[mass number]]s ranging from 86 to 122.{{NUBASE2020|ref}} Most of these have half-lives that are less than an hour, the exceptions being technetium-93 (2.73&nbsp;hours), technetium-94 (4.88&nbsp;hours), technetium-95 (20&nbsp;hours), and technetium-96 (4.3&nbsp;days).<ref name=CRCisotopes/>

The primary [[decay mode]] for isotopes lighter than technetium-98 (<sup>98</sup>Tc) is [[electron capture]], producing [[molybdenum]] (''Z''&nbsp;=&nbsp;42).<ref name=NNDC/> For technetium-98 and heavier isotopes, the primary mode is [[Beta decay|beta emission]] (the emission of an [[electron]] or [[positron]]), producing [[ruthenium]] (''Z''&nbsp;=&nbsp;44), with the exception that technetium-100 can decay both by beta emission and electron capture.<ref name=NNDC>
{{cite web
 |editor-last = Sonzogni |editor-first=A.A.
 |title = Chart of nuclides
 |series = National Nuclear Data Center
 |publisher = [[Brookhaven National Laboratory]]
 |place = Brookhaven, NY
 |url = http://www.nndc.bnl.gov/chart/
 |access-date = 2009-11-11 |url-status = dead
 |archive-url = https://web.archive.org/web/20090825001001/http://www.nndc.bnl.gov/chart/
 |archive-date = 2009-08-25
}}
</ref><ref>
{{cite book
 |editor-last = Lide |editor-first=David R.
 |date = 2004–2005
 |section = Table of the isotopes
 |title = The CRC Handbook of Chemistry and Physics
 |place = Boca Raton, FL
 |publisher =CRC press
}}
</ref>

Technetium also has numerous [[nuclear isomer]]s, which are isotopes with one or more [[Excited state|excited]] nucleons. Technetium-97m (<sup>97m</sup>Tc; "m" stands for [[metastability]]) is the most stable, with a half-life of 91&nbsp;days and [[excited state|excitation energy]] 0.0965&nbsp;MeV.<ref name=CRCisotopes>
{{cite book
 |last = Holden  |first = N.E.
 |date = 2006
 |title = Handbook of Chemistry and Physics  |edition = 87th
 |editor-last = Lide |editor-first = D.R.
 |publisher = CRC Press
 |location = Boca Raton, FL
 |pages = 11‑88–11‑89
 |isbn = 978-0-8493-0487-3
}}
</ref>
This is followed by technetium-95m (61&nbsp;days, 0.03&nbsp;MeV), and technetium-99m (6.01&nbsp;hours, 0.142&nbsp;MeV).<ref name="CRCisotopes" />

Technetium-99 (<sup>99</sup>Tc) is a major product of the fission of uranium-235 (<sup>235</sup>U), making it the most common and most readily available isotope of technetium. One gram of technetium-99 produces {{nobr|6.2 × {{10^|8}} disintegrations}} per second (in other words, the [[specific activity]] of <sup>99</sup>Tc is 0.62&nbsp;G[[Becquerel|Bq]]/g).<ref name=enc/>