Isotopes of mendelevium

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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 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[edit]

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[edit]

  • 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[edit]

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[edit]

  1. ^ http://www.nucleonica.net/unc.aspx
  2. ^ see nobelium


Isotopes of fermium Isotopes of mendelevium Isotopes of nobelium
Table of nuclides