Nobelium-251

Properties and data of the isotope ²⁵¹No.

Contents

General data

Name of the isotope:Nobelium-251; No-251Symbol:²⁵¹No or 251102NoMass 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-251)Nuclide 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)Separation energy:S_N = 6.79(23) MeV (first neutron)
S_P = 3.07(32) MeV (first proton)Half-life:0.80(1) sDecay constant λ:0.86643397569993 s^-1Specific activity α:2.078799779880 × 10⁺²¹ Bq g^-1
56183777834.608 Ci g^-1Spin and parity:
(nuclear angular momentum)(7/2+)Year of discovery:1967

Radioactive Decay

Half-life T_½ = 0.80(1) s respectively 8 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy
EE/β⁺	²⁵¹Md	?	3.88(12) MeV
α	²⁴⁷Fm	91 %	8.752(4) MeV
SF	div	< 0.3 %

Parent Nuclides

Direct parent isotope is: ²⁵⁵Rf.

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
^251mNo	106(6) keV	1.02(3) s	(1/2+)

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-251. 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