Isotopes of mendelevium

Mendelevium (Md) is an artificial 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 18 known radioisotopes, ranging in atomic mass from ²⁴⁵Md to ²⁶²Md, 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
nuclide symbol	excitation energy			half-life	decay mode(s)^[1]^{[n 1]}	daughter isotope(s)	nuclear spin
²⁴⁵Md	101	144	245.08083(35)#	0.90(25) ms	SF	(various)	(1/2-)#
²⁴⁵Md	101	144	245.08083(35)#	0.90(25) ms	α (rare)	²⁴¹Es	(1/2-)#
^245mMd	200(100)# keV			400(200) ms [0.35(+23-16) s]	α	²⁴¹Es	(7/2+)
^245mMd	200(100)# keV			400(200) ms [0.35(+23-16) s]	β⁺ (rare)	²⁴⁵Fm	(7/2+)
²⁴⁶Md	101	145	246.08189(35)#	1.0(4) s	α	²⁴²Es
²⁴⁶Md	101	145	246.08189(35)#	1.0(4) s	β⁺ (rare)	²⁴⁶Fm
²⁴⁷Md	101	146	247.08164(35)#	1.12(22) s	SF	(various)	1/2-#
²⁴⁷Md	101	146	247.08164(35)#	1.12(22) s	α (rare)	²⁴³Es	1/2-#
^247mMd				~0.2 s	α (99.99%)	²⁴³Es
^247mMd				~0.2 s	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	249.08301(24)#	24(4) s	α (60%)	²⁴⁵Es	(7/2-)
²⁴⁹Md	101	148	249.08301(24)#	24(4) s	β⁺ (40%)	²⁴⁹Fm	(7/2-)
^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	251.08484(22)#	4.0(5) min	β⁺ (90%)	²⁵¹Fm	7/2-#
²⁵¹Md	101	150	251.08484(22)#	4.0(5) min	α (10%)	²⁴⁷Es	7/2-#
²⁵²Md	101	151	252.08656(21)#	2.3(8) min	β⁺ (50%)	²⁵²Fm
²⁵²Md	101	151	252.08656(21)#	2.3(8) min	α (50%)	²⁴⁸Es
²⁵³Md	101	152	253.08728(22)#	12(8) min [6(+12-3) min]	β⁺	²⁵³Fm	7/2-#
²⁵³Md	101	152	253.08728(22)#	12(8) min [6(+12-3) min]	α	²⁴⁹Es	7/2-#
²⁵⁴Md	101	153	254.08966(11)#	10(3) min	β⁺	²⁵⁴Fm	(0-)
²⁵⁴Md	101	153	254.08966(11)#	10(3) min	α (rare)	²⁵⁰Es	(0-)
^254mMd	50(100)# keV			28(8) min	β⁺	²⁵⁴Fm	(3-)
^254mMd	50(100)# keV			28(8) min	α (rare)	²⁵⁰Es	(3-)
²⁵⁵Md	101	154	255.091083(7)	27(2) min	β⁺ (92%)	²⁵⁵Fm	(7/2-)
					α (8%)	²⁵¹Es
					SF (.15%)	(various)
²⁵⁶Md	101	155	256.09406(6)	77(2) min	β⁺ (89%)	²⁵⁶Fm	(1-)
²⁵⁶Md	101	155	256.09406(6)	77(2) min	α (11%)	²⁵²Es	(1-)
²⁵⁷Md	101	156	257.095541(3)	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	101	158	259.10051(22)#	1.60(6) h	SF (98.7%)	(various)	7/2-#
²⁵⁹Md	101	158	259.10051(22)#	1.60(6) h	α (1.3%)	²⁵⁵Es	7/2-#
²⁶⁰Md	101	159	260.10365(34)#	27.8(8) d	SF (85%)	(various)
					α (5%)	²⁵⁶Es
					EC (5%)	²⁶⁰Fm
					β^- (3.5%)	²⁶⁰No
²⁶¹Md	101	160	261.10572(70)#	40# min			7/2-#
²⁶²Md	101	161	262.10887(63)#	3# min

^ Abbreviations:
EC: Electron capture
IT: Isomeric transition
SF: Spontaneous fission

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.

References

^ http://www.nucleonica.net/unc.aspx

Isotope masses from:
- G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (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. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf.
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 and 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. http://www.iupac.org/publications/pac/75/6/0683/pdf/.
- 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. http://iupac.org/publications/pac/78/11/2051/pdf/. 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 and O. Bersillon (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. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf.
- National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. http://www.nndc.bnl.gov/nudat2/. Retrieved September 2005.
- 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 978-0849304859.

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