See also: List of individual Osmium isotopes (and general data sources).
General data
Name of the isotope:Osmium-186; Os-186Symbol:186Os or 18676OsMass number A:186 (= number of nucleons)Atomic number Z:76 (= number of protons)Neutrons N:110Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.4473684210526 (= neutron-proton ratio)Neutron excess (N-Z):34Isotopic mass:185.95384(1) u (atomic weight of Osmium-186)Nuclide mass:185.9121522 u (calculated nuclear mass without electrons)Mass excess:-42.99776 MeVMass defect:1.594003192 u (per nucleus)Nuclear binding energy:1484.80440933 MeV (per nucleus) 7.9828194 MeV (average binding energy per nucleon)Separation energy:SN = 8.2654(9) MeV (first neutron) SP = 6.4699(8) MeV (first proton)Half-life:2.0(11) × 1015 yearsDecay constant λ:1.0989776454844 × 10-23 s-1Specific activity α:0.035590542648652 Bq g-1 9.6190655807168 × 10-13 Ci g-1Spin and parity: (nuclear angular momentum)0+Charge radius:5.3909(17) femtometer fmYear of discovery:1931
Radioactive Decay
Half-life T½ = 2.0(11) × 1015 years respectively 6.3072 × 1022 seconds s.
Comparison of the natural Osmium isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):
Atomic Mass ma
Quantity
Half-life
Spin
Osmium Isotopic mixture
190.23 u
100 %
Isotope 184Os
183.952489(9) u
0.02(1) %
5.6 × 1013 years
0+
Isotope 186Os
185.95384(1) u
1.59(3) %
2.0(11) × 1015 years
0+
Isotope 187Os
186.95575(1) u
1.96(2) %
stable
1/2-
Isotope 188Os
187.95584(1) u
13.24(8) %
stable
0+
Isotope 189Os
188.95814(2) u
16.15(5) %
stable
3/2-
Isotope 190Os
189.95844(2) u
26.26(2) %
stable
0+
Isotope 192Os
191.96148(2) u
40.78(19) %
stable
0+
Isotones and Isobars
The following table shows the atomic nuclei that are isotonic (same neutron number N = 110) and isobaric (same nucleon number A = 186) with Osmium-186. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
