Isotopes of mendelevium

Mendelevium (Md) is a synthetic element, and thus a standard atomic mass 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 16 known radioisotopes, ranging in atomic mass from ²⁴⁵Md 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 58.0 minutes.

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)[1][n 1]	daughter isotope(s)	nuclear spin
	excitation energy
^245Md	101	144	245.08081(33)#	0.90(25) ms	SF	(various)	(1/2−)#
					α (rare)	^241Es
^245mMd	200(100)# keV			400(200) ms [0.35(+23−16) s]	α	^241Es	(7/2+)
					β^+ (rare)	^245Fm
^246Md	101	145	246.08171(28)#	1.0(4) s	α	^242Es
					β^+ (rare)	^246Fm
^247Md	101	146	247.08152(22)#	1.12(22) s	SF	(various)	1/2−#
					α (rare)	^243Es
^247mMd				~0.2 s	α (99.99%)	^243Es
					SF (10^−4%)	(various)
^248Md	101	147	248.08282(26)#	7(3) s	β^+ (80%)	^248Fm
					α (20%)	^244Es
					β^+, SF (.05%)	(various)
^249Md	101	148	249.08291(22)#	24(4) s	α (60%)	^245Es	(7/2−)
					β^+ (40%)	^249Fm
^249mMd	100(100)# keV			1.9(9) s			(1/2−)
^250Md	101	149	250.08442(32)#	52(6) s	β^+ (93%)	^250Fm
					α (7%)	^246Es
					β^+, SF (.02%)	(various)
^251Md	101	150	251.084774(20)	4.0(5) min	β^+ (90%)	^251Fm	7/2−#
					α (10%)	^247Es
^252Md	101	151	252.08643(14)#	2.3(8) min	β^+ (50%)	^252Fm
					α (50%)	^248Es
^253Md	101	152	253.08714(3)#	12(8) min [6(+12−3) min]	β^+	^253Fm	7/2−#
					α	^249Es
^254Md	101	153	254.08959(11)#	10(3) min	β^+	^254Fm	(0−)
					α (rare)	^250Es
^254mMd	50(100)# keV			28(8) min	β^+	^254Fm	(3−)
					α (rare)	^250Es
^255Md	101	154	255.091084(7)	27(2) min	β^+ (92%)	^255Fm	(7/2−)
					α (8%)	^251Es
					SF (.15%)	(various)
^256Md	101	155	256.09389(13)#	77(2) min	β^+ (89%)	^256Fm	(1−)
					α (11%)	^252Es
^257Md	101	156	257.0955424(29)	5.52(5) h	EC (84.8%)	^257Fm	(7/2−)
					α (15.2%)	^253Es
					SF (1%)	(various)
^258Md	101	157	258.098431(5)	51.5(3) d	α (99.99%)	^254Es	(8−)#
					β^− (.0015%)	^258No
					β^+ (.0015%)	^258Fm
^258mMd	0(200)# keV			57.0(9) min	EC (70%)	^258Fm	1−#
					SF (20%)	(various)
					β^− (10%)	^258No
					α (1.2%)	^254Es
^259Md[n 2]	101	158	259.10051(22)#	1.60(6) h	SF (98.7%)	(various)	7/2−#
					α (1.3%)	^255Es
^260Md	101	159	260.10365(34)#	27.8(8) d	SF (85%)	(various)
					α (5%)	^256Es
					EC (5%)	^260Fm
					β^− (3.5%)	^260No

1. Abbreviations:
   EC: Electron capture
   IT: Isomeric transition
   SF: Spontaneous fission
2. Not directly synthesized, occurs as decay product of ²⁵⁹No

Notes

• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.

Chronology of isotope discovery

Isotope	Discovered	Reaction
^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)[2]
^260Md	1989	^254Es+^18O, ^22Ne — transfer

References

1. "Universal Nuclide Chart". nucleonica. (registration required (help)).
2. 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.
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
• Isotopic compositions and standard atomic masses from:
  • J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary.
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005. Check date values in: |access-date= (help)
  • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.
  • M. Thoennessen (2012). "Discovery of Isotopes of Elements with Z≥100". arXiv:1203.2105.