Cobalt-55

Properties and data of the isotope ⁵⁵Co.

Content

General data

Name of the isotope:Cobalt-55; Co-55Symbol:⁵⁵Co or 5527CoMass number A:55 (= number of nucleons)Atomic number Z:27 (= number of protons)Neutrons N:28Isotopic mass:54.9419965(5) u (atomic weight of Cobalt-55)Nuclide mass:54.9271852 u (calculated nuclear mass without electrons)Mass excess:-54.02991 MeVMass defect:0.511897012 u (per nucleus)Nuclear binding energy:476.8289953 MeV (per nucleus)
8.6696181 MeV (average binding energy per nucleon)Separation energy:S_N = 14.0912(3) MeV (first neutron)
S_P = 5.0643(3) MeV (first proton)Half-life:17.53(3) hDecay constant λ:1.098350732965 × 10^-5 s^-1Specific activity α:1.2248931162 × 10⁺¹⁷ Bq g^-1
3310521.9357027 Ci g^-1Spin and parity:
(nuclear angular momentum)7/2-Magnetic dipole moment:μ(μ_N) = + 4.822(3)Nuclear g-factor:g_l = 1.3777142857143Mirror nucleus:Nickel-55Year of discovery:1938

Radioactive Decay

Half-life T_½ = 17.53(3) h (hours) respectively 6.3108 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE β⁺	⁵⁵Fe	100 %	3.4514(5) MeV

Parent Nuclides

Direct parent isotope is: ⁵⁵Ni.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 28) and isobaric (same nucleon number A = 55) with Cobalt-55. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 28	Isobar A = 55
11	³⁹Na
12	⁴⁰Mg
13	⁴¹Al
14	⁴²Si
15	⁴³P
16	⁴⁴S
17	⁴⁵Cl
18	⁴⁶Ar
19	⁴⁷K	⁵⁵K
20	⁴⁸Ca	⁵⁵Ca
21	⁴⁹Sc	⁵⁵Sc
22	⁵⁰Ti	⁵⁵Ti
23	⁵¹V	⁵⁵V
24	⁵²Cr	⁵⁵Cr
25	⁵³Mn	⁵⁵Mn
26	⁵⁴Fe	⁵⁵Fe
27	⁵⁵Co	⁵⁵Co
28	⁵⁶Ni	⁵⁵Ni
29	⁵⁷Cu	⁵⁵Cu
30	⁵⁸Zn	⁵⁵Zn
31	⁵⁹Ga
32	⁶⁰Ge