Mendelevium-255

Properties and data of the isotope ²⁵⁵Md.

Content

General data

Name of the isotope:Mendelevium-255; Md-255Symbol:²⁵⁵Md or 255101MdMass number A:255 (= number of nucleons)Atomic number Z:101 (= number of protons)Neutrons N:154Isotopic mass:255.091083(7) u (atomic weight of Mendelevium-255)Nuclide mass:255.0356847 u (calculated nuclear mass without electrons)Mass excess:84.84327 MeVMass defect:2.033642296 u (per nucleus)Nuclear binding energy:1894.32559687 MeV (per nucleus)
7.42872783 MeV (average binding energy per nucleon)Separation energy:S_N = 6.68(10) MeV (first neutron)
S_P = 3.349(7) MeV (first proton)Half-life:27(2) minDecay constant λ:0.00042786862997527 s^-1Specific activity α:1.01046476833 × 10⁺¹⁸ Bq g^-1
27309858.603703 Ci g^-1Spin and parity:
(nuclear angular momentum)(7/2-)Year of discovery:1958

Radioactive Decay

Half-life T_½ = 27(2) min (minutes) respectively 1.620 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	²⁵⁵Fm	93(1) %	1.043(8) MeV
α	²⁵¹Es	7(1) %	7.9059(26) MeV

Parent Nuclides

Direct parent isotopes are: ²⁵⁹Lr, ²⁵⁵No.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 154) and isobaric (same nucleon number A = 255) with Mendelevium-255. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 154	Isobar A = 255
95	²⁴⁹Am
96	²⁵⁰Cm
97	²⁵¹Bk
98	²⁵²Cf	²⁵⁵Cf
99	²⁵³Es	²⁵⁵Es
100	²⁵⁴Fm	²⁵⁵Fm
101	²⁵⁵Md	²⁵⁵Md
102	²⁵⁶No	²⁵⁵No
103	²⁵⁷Lr	²⁵⁵Lr
104	²⁵⁸Rf	²⁵⁵Rf
105	²⁵⁹Db	²⁵⁵Db
106	²⁶⁰Sg
107	²⁶¹Bh