Nobelium-257

Properties and data of the isotope ²⁵⁷No.

Contents

General data

Name of the isotope:Nobelium-257; No-257Symbol:²⁵⁷No or 257102NoMass number A:257 (= number of nucleons)Atomic number Z:102 (= number of protons)Neutrons N:155Isotopic mass:257.096884(7) u (atomic weight of Nobelium-257)Nuclide mass:257.0409373 u (calculated nuclear mass without electrons)Mass excess:90.24686 MeVMass defect:2.044331244 u (per nucleus)Nuclear binding energy:1904.2822878 MeV (per nucleus)
7.40965871 MeV (average binding energy per nucleon)Separation energy:S_N = 5.646(10) MeV (first neutron)
S_P = 4.50(12) MeV (first proton)Half-life:24.5(5) sDecay constant λ:0.028291721655508 s^-1Specific activity α:6.629444863019 × 10⁺¹⁹ Bq g^-1
1791741854.87 Ci g^-1Spin and parity:
(nuclear angular momentum)(3/2+)Year of discovery:1967

Radioactive Decay

Half-life T_½ = 24.5(5) s respectively 2.45 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy
α	²⁵³Fm	85(15) %	8.477(6) MeV
EE	²⁵⁷Md	≤ 30 %	1.254(7) MeV
SZ	div.	< 1.5 %

Parent Nuclides

Direct parent isotope is: ²⁶¹Rf.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 155) and isobaric (same nucleon number A = 257) with Nobelium-257. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 155	Isobar A = 257
96	²⁵¹Cm
97	²⁵²Bk
98	²⁵³Cf
99	²⁵⁴Es	²⁵⁷Es
100	²⁵⁵Fm	²⁵⁷Fm
101	²⁵⁶Md	²⁵⁷Md
102	²⁵⁷No	²⁵⁷No
103	²⁵⁸Lr	²⁵⁷Lr
104	²⁵⁹Rf	²⁵⁷Rf
105	²⁶⁰Db	²⁵⁷Db
106	²⁶¹Sg
107	²⁶²Bh
108	²⁶³Hs