Nobelium-256

Properties and data of the isotope ²⁵⁶No.

Contents

General data

Name of the isotope:Nobelium-256; No-256Symbol:²⁵⁶No or 256102NoMass number A:256 (= number of nucleons)Atomic number Z:102 (= number of protons)Neutrons N:154Isotopic mass:256.094281(8) u (atomic weight of Nobelium-256)Nuclide mass:256.0383343 u (calculated nuclear mass without electrons)Mass excess:87.82219 MeVMass defect:2.038269328 u (per nucleus)Nuclear binding energy:1898.63564942 MeV (per nucleus)
7.41654551 MeV (average binding energy per nucleon)Separation energy:S_N = 7.056(17) MeV (first neutron)
S_P = 4.31(1) MeV (first proton)Half-life:2.91(5) sDecay constant λ:0.23819490740892 s^-1Specific activity α:5.603294080219 × 10⁺²⁰ Bq g^-1
15144038054.646 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Year of discovery:1963

Radioactive Decay

Half-life T_½ = 2.91(5) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁵²Fm	99.47(6) %	8.582(5) MeV
SZ	div.	0.53(6) %

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 154) and isobaric (same nucleon number A = 256) with Nobelium-256. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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