Lawrencium-255

Properties and data of the isotope ²⁵⁵Lr.

Content

General data

Name of the isotope:Lawrencium-255; Lr-255Symbol:²⁵⁵Lr or 255103LrMass number A:255 (= number of nucleons)Atomic number Z:103 (= number of protons)Neutrons N:152Isotopic mass:255.096562(19) u (atomic weight of Lawrencium-255)Nuclide mass:255.040067 u (calculated nuclear mass without electrons)Mass excess:89.94692 MeVMass defect:2.026483528 u (per nucleus)Nuclear binding energy:1887.65724743 MeV (per nucleus)
7.40257744 MeV (average binding energy per nucleon)Separation energy:S_N = 8.0(3) MeV (first neutron)
S_P = 2.065(20) MeV (first proton)Half-life:31.1(11) sDecay constant λ:0.022287690693246 s^-1Specific activity α:5.263514227350 × 10⁺¹⁹ Bq g^-1
1422571412.7973 Ci g^-1Spin and parity:
(nuclear angular momentum)(1/2-)Year of discovery:1971

Radioactive Decay

Half-life T_½ = 31.1(11) s respectively 3.11 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy
α	²⁵¹Md	99.7(1) %	8.556(7) MeV
EE	²⁵⁵No	< 0.3(1) %	3.140(23) MeV
SF	^div.	< 0.1 %

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
^255m1Lr	38(10) keV	2.54(5) s	(7/2-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 152) and isobaric (same nucleon number A = 255) with Lawrencium-255. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 152	Isobar A = 255
94	²⁴⁶Pu
95	²⁴⁷Am
96	²⁴⁸Cm
97	²⁴⁹Bk
98	²⁵⁰Cf	²⁵⁵Cf
99	²⁵¹Es	²⁵⁵Es
100	²⁵²Fm	²⁵⁵Fm
101	²⁵³Md	²⁵⁵Md
102	²⁵⁴No	²⁵⁵No
103	²⁵⁵Lr	²⁵⁵Lr
104	²⁵⁶Rf	²⁵⁵Rf
105	²⁵⁷Db	²⁵⁵Db
106	²⁵⁸Sg