Boron-21
Properties and data of the isotope 21B.
See also: list of Boron isotopes.
General data
Name of the isotope:Boron-21; B-21Symbol:21B or 215BMass number A:21 (= number of nucleons)Atomic number Z:5 (= number of protons)Neutrons N:16Isotopic mass:21.08302(97) u (atomic weight of Boron-21)Nuclide mass:21.0802771 u (calculated nuclear mass without electrons)Mass excess:77.33263 MeVMass defect:0.094743816000001 u (per nucleus)Nuclear binding energy:88.25329614 MeV (per nucleus)
4.20253791 MeV (average binding energy per nucleon)Half-life:< 260 nsDecay constant λ:2665950.6944613 s-1Specific activity α:7.645109813186 × 10+28 Bq g-1
2.066245895455 × 10+18 Ci g-1Spin and parity:
(nuclear angular momentum)(3/2-)Year of discovery:2018
Radioactive Decay
Half-life T½ = < 260 ns respectively 2.6 × 10-7 seconds s.
Decay mode | Daughter | Probability | Decay energy | γ energy (intensity) |
---|
2n | 19B | | | |
Isotones and Isobars
The following table shows the atomic nuclei that are isotonic (same neutron number N = 16) and isobaric (same nucleon number A = 21) with Boron-21. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
OZ | Isotone N = 16 | Isobar A = 21 |
5 | 21B | 21B |
6 | 22C | 21C |
7 | 23N | 21N |
8 | 24O | 21O |
9 | 25F | 21F |
10 | 26Ne | 21Ne |
11 | 27Na | 21Na |
12 | 28Mg | 21Mg |
13 | 29Al | 21Al |
14 | 30Si | |
15 | 31P | |
16 | 32S | |
17 | 33Cl | |
18 | 34Ar | |
19 | 35K | |
20 | 36Ca | |
21 | 37Sc | |
22 | 38Ti | |
External data and identifiers
Literature and References
[1] - S. Leblond et al.:
First Observation of 20B and 21B.
In: Physical Review Letters, (2018), DOI 10.1103/PhysRevLett.121.262502.
Last update: 2020-10-11
Perma link: https://www.chemlin.org/isotope/boron-21
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