Isotopes of mendelevium explained

Mendelevium (₁₀₁Md) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was ²⁵⁶Md (which was also the first isotope of any element produced one atom at a time) in 1955. There are 17 known radioisotopes, ranging in atomic mass from ²⁴⁴Md to ²⁶⁰Md, and 5 isomers. The longest-lived isotope is ²⁵⁸Md with a half-life of 51.3 days, and the longest-lived isomer is ^258mMd with a half-life of 57 minutes.

List of isotopes

|-| rowspan=2|²⁴⁴Md| rowspan=2 style="text-align:right" | 101| rowspan=2 style="text-align:right" | 143| rowspan=2|244.08116(40)#| rowspan=2|0.36(14) s| α| ²⁴⁰Es| rowspan=2|3+#|-| β⁺, SF (<14%)| (various)|-id=Mendelevium-244m| style="text-indent:1em" | ^244mMd| colspan="3" style="text-indent:2em" | 200(150)# keV| ~9 μs| IT| ²⁴⁴Md| 7+#|-id=Mendelevium-245| ²⁴⁵Md| style="text-align:right" | 101| style="text-align:right" | 144| 245.08086(28)#| 0.38(10) s| α| ²⁴¹Es| (7/2−)|-id=Mendelevium-245m| style="text-indent:1em" | ^245mMd^[1] | colspan="3" style="text-indent:2em" | 100(100)# keV| 0.90(25) ms| SF| (various)| 1/2−#|-id=Mendelevium-246| ²⁴⁶Md| style="text-align:right" | 101| style="text-align:right" | 145| 246.08171(28)#| 0.92(18) s| α| ²⁴²Es| 1−#|-id=Mendelevium-246m| rowspan=3 style="text-indent:1em" | ^246mMd^[1] | rowspan=3 colspan="3" style="text-indent:2em" | 60(60) keV| rowspan=3|4.4(8) s| β⁺ (~67%)| ²⁴⁶Fm| rowspan=3|4−#|-| α (<23%)| ²⁴²Es|-| β⁺, SF (>10%)| (various)|-| rowspan=2|²⁴⁷Md^[2] | rowspan=2 style="text-align:right" | 101| rowspan=2 style="text-align:right" | 146| rowspan=2|247.08152(22)#| rowspan=2|1.20(12) s| α (99.14%)| ²⁴³Es| rowspan=2|(7/2−)|-| SF (0.86%)| (various)|-id=Mendelevium-247m| rowspan=2 style="text-indent:1em" | ^247mMd| rowspan=2 colspan="3" style="text-indent:2em" | 153 keV| rowspan=2|0.23(3) s| α (80%)| ²⁴³Es| rowspan=2|(1/2−)|-| SF (20%)| (various)|-| rowspan=3|²⁴⁸Md| rowspan=3 style="text-align:right" | 101| rowspan=3 style="text-align:right" | 147| rowspan=3|248.08261(20)#| rowspan=3|7(3) s| β⁺ (80%)| ²⁴⁸Fm| rowspan=3||-| α (20%)| ²⁴⁴Es|-| β⁺, SF (<0.05%)| (various)|-| rowspan=2|²⁴⁹Md| rowspan=2 style="text-align:right" | 101| rowspan=2 style="text-align:right" | 148| rowspan=2|249.08286(18)| rowspan=2|25.6(9) s| α (75%)| ²⁴⁵Es| rowspan=2|(7/2−)|-| β⁺ (25%)| ²⁴⁹Fm|-id=Mendelevium-249m| style="text-indent:1em" | ^249mMd^[1] | colspan="3" style="text-indent:2em" | 100(100)# keV| 1.9(9) s| α| ²⁴⁵Es| (1/2−)|-| rowspan=3|²⁵⁰Md| rowspan=3 style="text-align:right" | 101| rowspan=3 style="text-align:right" | 149| rowspan=3|250.084165(98)| rowspan=3|54(4) s| β⁺ (93.0%)| ²⁵⁰Fm| rowspan=3|2−#|-| α (7.0%)| ²⁴⁶Es|-| β⁺, SF (0.026%)| (various)|-id=Mendelevium-250m| style="text-indent:1em" | ^250mMd| colspan="3" style="text-indent:2em" | 120(40) keV| 42.4(45) s| α| ²⁴⁶Es| 7+#|-| rowspan=2|²⁵¹Md| rowspan=2 style="text-align:right" | 101| rowspan=2 style="text-align:right" | 150| rowspan=2|251.084774(20)| rowspan=2|4.21(23) min| β⁺ (90%)| ²⁵¹Fm| rowspan=2|(7/2−)|-| α (10%)| ²⁴⁷Es|-id=Mendelevium-251m| style="text-indent:1em" | ^251mMd| colspan="3" style="text-indent:2em" | 53(8) keV| 20# s| | | (1/2−)|-id=Mendelevium-252| ²⁵²Md| style="text-align:right" | 101| style="text-align:right" | 151| 252.086385(98)| 2.3(8) min| β⁺| ²⁵²Fm| 1+#|-| rowspan=2|²⁵³Md| rowspan=2 style="text-align:right" | 101| rowspan=2 style="text-align:right" | 152| rowspan=2|253.087143(34)#| rowspan=2|12(8) min| β⁺ (~99.3%)| ²⁵³Fm| rowspan=2|(7/2−)|-| α (~0.7%)| ²⁴⁹Es|-id=Mendelevium-253m| style="text-indent:1em" | ^253mMd| colspan="3" style="text-indent:2em" | 60(30) keV| 1# min| | | (1/2−)|-id=Mendelevium-254| ²⁵⁴Md| style="text-align:right" | 101| style="text-align:right" | 153| 254.08959(11)#| 10(3) min| β⁺| ²⁵⁴Fm| 0−#|-id=Mendelevium-254m| style="text-indent:1em" | ^254mMd^[1] | colspan="3" style="text-indent:2em" | 50(100)# keV| 28(8) min| β⁺| ²⁵⁴Fm| 3−#|-| rowspan=2|²⁵⁵Md| rowspan=2 style="text-align:right" | 101| rowspan=2 style="text-align:right" | 154| rowspan=2|255.0910817(60)| rowspan=2|27(2) min| β⁺ (93%)| ²⁵⁵Fm| rowspan=2|7/2−|-| α (7%)| ²⁵¹Es|-| rowspan=3|²⁵⁶Md| rowspan=3 style="text-align:right" | 101| rowspan=3 style="text-align:right" | 155| rowspan=3|256.09389(13)#| rowspan=3|77.7(18) min| β⁺ (90.8%)| ²⁵⁶Fm| rowspan=3|(1−)|-| α (9.2%)| ²⁵²Es|-| SF (<3%)| (various)|-| rowspan=2|²⁵⁷Md| rowspan=2 style="text-align:right" | 101| rowspan=2 style="text-align:right" | 156| rowspan=2|257.0955373(17)| rowspan=2|5.52(5) h| EC (85%)| ²⁵⁷Fm| rowspan=2|(7/2−)|-| α (15%)| ²⁵³Es|-| rowspan=3|²⁵⁸Md| rowspan=3 style="text-align:right" | 101| rowspan=3 style="text-align:right" | 157| rowspan=3|258.0984336(37)| rowspan=3|51.59(29) d| α| ²⁵⁴Es| rowspan=3|(8−)#|-| β⁻ (<0.0015%)| ²⁵⁸No|-| β⁺ (<0.0015%)| ²⁵⁸Fm|-id=Mendelevium-258m| rowspan=3 style="text-indent:1em" | ^258mMd^[1] | rowspan=3 colspan="3" style="text-indent:2em" | 0(200)# keV| rowspan=3|57.0(9) min| EC (85%)| ²⁵⁸Fm| rowspan=3|1−#|-| SF (<15%)| (various)|-| α (<1.2%)| ²⁵⁴Es|-id=Mendelevium-259| ²⁵⁹Md^[3] | style="text-align:right" | 101| style="text-align:right" | 158| 259.10045(11)#| 1.60(6) h| SF| (various)| 7/2−#|-| rowspan=4|²⁶⁰Md| rowspan=4 style="text-align:right" | 101| rowspan=4 style="text-align:right" | 159| rowspan=4|260.10365(34)#| rowspan=4|27.8(8) d| SF| (various)| rowspan=4||-| α (<5%)| ²⁵⁶Es|-| EC (<5%)| ²⁶⁰Fm|-| β⁻ (<3.5%)| ²⁶⁰No

Chronology of isotope discovery

Isotope	Discovered	Reaction
²⁴⁴Md	2020	²⁰⁹Bi(⁴⁰Ar,5n)
²⁴⁵Md	1996	²⁰⁹Bi(⁴⁰Ar,4n)
²⁴⁶Md	1996	²⁰⁹Bi(⁴⁰Ar,3n)
²⁴⁷Md	1981	²⁰⁹Bi(⁴⁰Ar,2n)
²⁴⁸Md	1973	²⁴¹Am(¹²C,5n)
²⁴⁹Md	1973	²⁴¹Am(¹²C,4n)
²⁵⁰Md	1973	²⁴³Am(¹²C,5n), ²⁴³Am(¹³C,6n)
²⁵¹Md	1973	²⁴³Am(¹²C,4n), ²⁴³Am(¹³C,5n)
²⁵²Md	1973	²⁴³Am(¹³C,4n)
²⁵³Md	1992	²⁴³Am(¹³C,3n)
²⁵⁴Md	1970	²⁵³Es(α,3n)
²⁵⁵Md	1958	²⁵³Es(α,2n)
²⁵⁶Md	1955	²⁵³Es(α,n)
²⁵⁷Md	1964	²⁵²Cf(¹¹B,α2n)
²⁵⁸Md	1970	²⁵⁵Es(α,n)
²⁵⁹Md	1982	²⁴⁸Cm(¹⁸O,α3n)^[4]
²⁶⁰Md	1989	²⁵⁴Es+¹⁸O, ²²Ne — transfer

References

Isotope masses from:
- M. Wang . G. Audi . A. H. Wapstra . F. G. Kondev . M. MacCormick . X. Xu. 2012 . The AME2012 atomic mass evaluation (II). Tables, graphs and references. . Chinese Physics C . 36 . 12 . 1603–2014 . 10.1088/1674-1137/36/12/003. 2012ChPhC..36....3M . 250839471 . etal.
  - Half-life, spin, and isomer data selected from the following sources.
    - - M. Thoennessen . 2012 . Discovery of Isotopes of Elements with Z≥100 . 1203.2105 . 10.1016/j.adt.2012.03.003 . 99 . 3 . Atomic Data and Nuclear Data Tables . 312–344. 2013ADNDT..99..312T . 94982856 .

Notes and References

Order of ground state and isomer is uncertain.
Heßberger . F. P. . Antalic . S. . Giacoppo . F. . Andel . B. . Ackermann . D. . Block . M. . Heinz . S. . Khuyagbaatar . J. . Kojouharov . I. . Venhart . M. . Alpha-gamma decay studies of ²⁴⁷Md . The European Physical Journal A . 25 January 2022 . 58 . 1 . 11 . 10.1140/epja/s10050-022-00663-4 . 2022EPJA...58...11H . 246281669 . 1434-601X. free .
Not directly synthesized, occurs as decay product of ²⁵⁹No
see nobelium