Isotopes of mendelevium

Isotopes of mendelevium (₁₀₁Md)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct ^256Md synth 77.7 min ε ^256Fm α ^252Es ^257Md synth 5.52 h ε ^257Fm α ^253Es SF – ^258Md synth 51.5 d α ^254Es ε ^258Fm β^− ^258No ^259Md synth 1.60 h SF – α ^255Es ^260Md synth 31.8 d SF – α ^256Es ε ^260Fm β^− ^260No

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

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

1. ^mMd – Excited nuclear isomer.
2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. Modes of decay:

   EC:	Electron capture
   SF:	Spontaneous fission

5. ( ) spin value – Indicates spin with weak assignment arguments.
6. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
7. Discovery of this isotope is disputed due to conflicting data.^[3]
8. Order of ground state and isomer is uncertain.
9. Not directly synthesized, occurs as decay product of ²⁵⁹No

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)[5]
^260Md	1989	^254Es+^18O, ^22Ne — transfer

References

1. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
2. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
3. Heßberger, F. P.; Block, M.; Düllmann, Ch. E.; Yakushev, A.; Leino, M.; Uusitalo, J. (3 May 2021). "Some Remarks on the Discovery of Md 244". Physical Review Letters. 126 (18). arXiv:2101.06076. doi:10.1103/PhysRevLett.126.182501.
4. Heßberger, F. P.; Antalic, S.; Giacoppo, F.; Andel, B.; Ackermann, D.; Block, M.; Heinz, S.; Khuyagbaatar, J.; Kojouharov, I.; Venhart, M. (25 January 2022). "Alpha-gamma decay studies of ²⁴⁷Md". The European Physical Journal A. 58 (1): 11. Bibcode:2022EPJA...58...11H. doi:10.1140/epja/s10050-022-00663-4. ISSN 1434-601X. S2CID 246281669.
5. see nobelium

• Isotope masses from:
  • M. Wang; G. Audi; A. H. Wapstra; F. G. Kondev; M. MacCormick; X. Xu; et al. (2012). "The AME2012 atomic mass evaluation (II). Tables, graphs and references" (PDF). Chinese Physics C. 36 (12): 1603–2014. Bibcode:2012ChPhC..36....3M. doi:10.1088/1674-1137/36/12/003. S2CID 250839471.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
• Half-life, spin, and isomer data selected from the following sources.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
  • National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
  • Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.
  • M. Thoennessen (2012). "Discovery of Isotopes of Elements with Z≥100". Atomic Data and Nuclear Data Tables. 99 (3): 312–344. arXiv:1203.2105. Bibcode:2013ADNDT..99..312T. doi:10.1016/j.adt.2012.03.003. S2CID 94982856.