Nobelium-255

Properties and data of the isotope ²⁵⁵No.

Content

General data

Name of the isotope:Nobelium-255; No-255Symbol:²⁵⁵No or 255102NoMass number A:255 (= number of nucleons)Atomic number Z:102 (= number of protons)Neutrons N:153Isotopic mass:255.093191(16) u (atomic weight of Nobelium-255)Nuclide mass:255.0372443 u (calculated nuclear mass without electrons)Mass excess:86.80686 MeVMass defect:2.030694412 u (per nucleus)Nuclear binding energy:1891.57966061 MeV (per nucleus)
7.41795945 MeV (average binding energy per nucleon)Separation energy:S_N = 5.987(18) MeV (first neutron)
S_P = 3.93(10) MeV (first proton)Half-life:3.52(21) minDecay constant λ:0.0032819468776513 s^-1Specific activity α:7.750724075311 × 10⁺¹⁸ Bq g^-1
209479029.06248 Ci g^-1Spin and parity:
(nuclear angular momentum)(1/2+)Year of discovery:1967

Radioactive Decay

Half-life T_½ = 3.52(21) min respectively 2.112 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	²⁵⁵Md	70(5) %	1.964(16) MeV
α	²⁵¹Fm	30(5) %	8.428(3) MeV

Parent Nuclides

Direct parent isotope is: ²⁵⁹Rf.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 153) and isobaric (same nucleon number A = 255) with Nobelium-255. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 153	Isobar A = 255
94	²⁴⁷Pu
95	²⁴⁸Am
96	²⁴⁹Cm
97	²⁵⁰Bk
98	²⁵¹Cf	²⁵⁵Cf
99	²⁵²Es	²⁵⁵Es
100	²⁵³Fm	²⁵⁵Fm
101	²⁵⁴Md	²⁵⁵Md
102	²⁵⁵No	²⁵⁵No
103	²⁵⁶Lr	²⁵⁵Lr
104	²⁵⁷Rf	²⁵⁵Rf
105	²⁵⁸Db	²⁵⁵Db
106	²⁵⁹Sg
107	²⁶⁰Bh