Nobelium-251m

Properties and data of the isotope ^251mNo.

Contents

General data

Name of the isotope:Nobelium-251m; No-251mSymbol:^251mNo or 251m102NoMass number A:251 (= number of nucleons)Atomic number Z:102 (= number of protons)Neutrons N:149Isotopic mass:251.08894(12) u (atomic weight of Nobelium-251m)
Excitation energy: 106(6) keVNuclide mass:251.0329933 u (calculated nuclear mass without electrons)Mass excess:82.84708 MeVMass defect:2.000285748 u (per nucleus)Nuclear binding energy:1863.25417255 MeV (per nucleus)
7.4233234 MeV (average binding energy per nucleon)Half-life:1.02(3) sDecay constant λ:0.6795560593725 s^-1Specific activity α:1.630431199906 × 10⁺²¹ Bq g^-1
44065708105.576 Ci g^-1Spin and parity:
(nuclear angular momentum)(1/2+)

Radioactive Decay

Half-life T_½ = 1.02(3) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁴⁷Fm	ca. 100 %

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
²⁵¹No		0.80(1) s	(7/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 149) and isobaric (same nucleon number A = 251) with Nobelium-251m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 149	Isobar A = 251
91	²⁴⁰Pa
92	²⁴¹U
93	²⁴²Np
94	²⁴³Pu
95	²⁴⁴Am
96	²⁴⁵Cm	²⁵¹Cm
97	²⁴⁶Bk	²⁵¹Bk
98	²⁴⁷Cf	²⁵¹Cf
99	²⁴⁸Es	²⁵¹Es
100	²⁴⁹Fm	²⁵¹Fm
101	²⁵⁰Md	²⁵¹Md
102	²⁵¹No	²⁵¹No
103	²⁵²Lr	²⁵¹Lr
104	²⁵³Rf