Isotopes of boron are varieties of atoms (and nuclei ) of a chemical element of boron having different neutron contents in the nucleus.
All boron isotopes have 5 protons in the nucleus.
Natural boron consists of two stable isotopes , boron-10 with a concentration of about 20 at.% And the rest is boron-11. The ratio of these two isotopes varies in different natural sources as a result of the natural processes of enrichment with one or another isotope. The concentrations of boron − 10 and boron-11 averaged over various natural sources of boron are 19.97 at.% And 80.17 at.%, Respectively, with variations ranging from 18.929–20.386 and 79.614–81.071 at.%, Respectively.
All other boron isotopes are radioactive , the most long-lived of them is boron-8 with a half-life of 770 ms.
Boron Isotope Table
| Designation isotope | N ( n ) [n 1] | Weight kernels but. e. m. [1] | Period half-life [width decay] [2] | Channel (s) decay (probability channel decay,%) [3] | Affiliated core | Nuclear spin and parity |
|---|---|---|---|---|---|---|
| 7 B | 2 | 7.029712 (27) [n 2] | 3.50 (50) × 10 −20 s [1.4 (2)] MeV | p | 6 Be [n 3] | (3 / 2−) [n 4] |
| 8 B [n 5] | 3 | 8,0246073 (11) | 770 (3) ms | β + , α | 2 4 He | 2+ |
| 9 B | four | 9,0133296 (10) | 8.00 (300) × 10 −16 s [0.54 (21) keV ] | p, α | 2 4 He | 3 / 2− |
| 10 B | five | 10,012936862 (16) | stable | 3+ | ||
| 11 B | 6 | 11,009305167 (13) | stable | 3 / 2− | ||
| 12 B | 7 | 12,0143526 (14) | 20.20 (2) ms | β - (98,4) | 12 C | 1+ |
| β - , α (1,6) | 8 Be [n 6] | |||||
| 13 B | eight | 13,0177800 (11) | 17.33 (17) ms | β - (99.72) | 13 C | 3 / 2− |
| β - , n (0.28) | 12 C | |||||
| 14 B | 9 | 14,025404 (23) | 12.5 (5) ms | β - (93.96) | 14 C | 2− |
| β - , n (6.04) | 13 C | |||||
| 15 B | ten | 15.031088 (23) | 9.93 (7) ms | β - , n (93.6) | 14 C | 3 / 2− |
| β - (6.0) | 15 C | |||||
| β - , 2n (0.4) | 13 C | |||||
| 16 B | eleven | 16,039842 (26) | > 4.6 × 10 −21 s [0.1 MeV] | n | 15 B | 0− |
| 17 B [n 7] | 12 | 17.04693 (22) | 5.08 (5) ms | β - , n (63,0) | 16 C | (3 / 2−) |
| β - (22,1) | 17 C | |||||
| β - , 2n (11.0) | 15 C | |||||
| β - , 3n (3,5) | 14 C | |||||
| β - , 4n (0.4) | 13 C | |||||
| 18 B | 13 | 18,05560 (22) | <26 ns | n | 17 B | (2−) |
| 19 B [n 7] | 14 | 19,06417 (56) | 2.92 (13) ms | β - , n (71) | 18 C | 3 / 2− # [n 8] |
| β - , 2n (17) | 17 C | |||||
| β - (12) | 19 C | |||||
| 20 B [4] | 15 | 20.07348 (86) # | [2.50 (9) MeV] | n | 19 B | (1−, 2−) |
| 21 B [4] | sixteen | 21.08302 (97) # | <260 ns [2.47 (19) MeV] | 2n | 19 B | (3/2 -) # |
- ↑ The number of neutrons in the nucleus.
- ↑ Unreliable experimental numbers are given in parentheses.
- ↑ Then it decays through double proton decay into the helium-4 ( 4 He ) nucleus according to the total reaction: 7 B → 4 He + 3 1 H.
- ↑ Spin and parity in parentheses are not reliably established.
- ↑ Has one weakly bound proton.
- ↑ The beryllium-8 nucleus immediately decomposes into two alpha particles, the total reaction equation: 12 B → 3 4 He + β - .
- ↑ 1 2 Has two weakly bound neutrons.
- ↑ The values marked with the # symbol are obtained not only from experimental data, partly from theoretical considerations.
Application
Boron-10 has a very high thermal neutron capture cross section of 3837 barn (for most isotopes this cross section is close to units or fractions of a barn), and when a neutron is captured, an excited boron-11 nucleus ( 11 B *) immediately decays into two stable nuclei ( alpha-particle and lithium-7 nucleus), these nuclei are very quickly inhibited in the medium, and penetrating radiation ( gamma radiation and neutrons) are absent, in contrast to similar neutron capture reactions by other isotopes:
- 10 B + n → 11 B * → 4 He + 7 Li + 2.31 MeV .
Therefore, 10 V in a solution of boric acid and other chemical compounds, for example, boron carbide, is used in nuclear reactors to regulate reactivity , as well as for biological protection of personnel from thermal neutrons. To increase the neutron absorption efficiency, boron, used in reactors, is sometimes specially enriched with boron-10 isotope.
In addition, boron compounds are used in neutron capture therapy for certain types of brain cancer ; the range of ionizing fast nuclei of helium-4 and lithium-7 in the body tissues is very small and therefore healthy tissues are not affected by ionizing radiation.
The gaseous chemical compound of boron BF 3 is used as a working medium in the ionization chambers of thermal neutron detectors .
In 2015, in an article published in the journal Science [5], it was proposed to use the measurement of the ratio of boron isotopes in ancient sedimentary rocks of the late Permian and the beginning of the Triassic periods to determine changes in the water acidity ( pH ) of the Paleo-oceans in those eras, to explain the possible causes of Permian mass extinction mainly aquatic organisms, probably caused by a global increase in volcanic activity, accompanied by the release of carbon dioxide into the atmosphere. This method for determining the retro-acidity of ancient oceans is apparently more accurate than the previously used method for determining acidity by the ratio of calcium isotopes [6] and carbon isotopes .
Notes
- ↑ Audi G. , Wapstra AH , Thibault C. The AME2003 atomic mass evaluation (II). Tables, graphs, and references (Eng.) // Nuclear Physics A. - 2003. - Vol. 729 . - P. 337–676 . - DOI : 10.1016 / j.nuclphysa.2003.11.003 . - .
- ↑ Audi G. , Bersillon O. , Blachot J. , Wapstra AH The NUBASE evaluation of nuclear and decay properties // Nuclear Physics A. - 2003 .-- T. 729 . - S. 3—128 . - DOI : 10.1016 / j.nuclphysa.2003.11.001 . - .
- ↑ Universal Nuclide Chart . Nucleonica.
- ↑ 1 2 Leblond, S. et al. First observation of 20 B and 21 B // Physical Review Letters : journal. - 2018 .-- Vol. 121 , no. 26 . - P. 262502-262501 . - DOI : 10.1103 / PhysRevLett.121.262502 . - arXiv : 1901.00455 . - PMID 30636115 .
- ↑ Clarkson, MO et al. (2015) Science 348, 229–232.
- ↑ Witze, Alexandra (2015) Acidic oceans linked to greatest extinction ever; Rocks from 252 million years ago suggest that carbon dioxide from volcanoes made sea water lethal. Journal Nature; News publiée le 09 avril 2015
| one H | 2 He | ||||||||||||||||
| 3 Li | four Be | five B | 6 C | 7 N | eight O | 9 F | ten Ne | ||||||||||
| eleven Na | 12 Mg | 13 Al | 14 Si | 15 P | sixteen S | 17 Cl | 18 Ar | ||||||||||
| nineteen K | 20 Ca | 21 Sc | 22 Ti | 23 V | 24 Cr | 25 Mn | 26 Fe | 27 Co | 28 Ni | 29th Cu | thirty Zn | 31 Ga | 32 Ge | 33 As | 34 Se | 35 Br | 36 Kr |
| 37 Rb | 38 Sr | 39 Y | 40 Zr | 41 Nb | 42 Mo | 43 Tc | 44 Ru | 45 Rh | 46 Pd | 47 Ag | 48 Cd | 49 In | 50 Sn | 51 Sb | 52 Te | 53 I | 54 Xe |
| 55 Cs | 56 Ba | * | 72 Hf | 73 Ta | 74 W | 75 Re | 76 Os | 77 Ir | 78 Pt | 79 Au | 80 Hg | 81 Tl | 82 Pb | 83 Bi | 84 Po | 85 At | 86 Rn |
| 87 Fr | 88 Ra | ** | 104 Rf | 105 Db | 106 Sg | 107 Bh | 108 Hs | 109 Mt | 110 Ds | 111 Rg | 112 Cn | 113 Nh | 114 Fl | 115 Mc | 116 Lv | 117 Ts | 118 Og |
| * | 57 La | 58 Ce | 59 Pr | 60 Nd | 61 Pm | 62 Sm | 63 Eu | 64 Gd | 65 Tb | 66 Dy | 67 Ho | 68 Er | 69 Tm | 70 Yb | 71 Lu |
| ** | 89 Ac | 90 Th | 91 Pa | 92 U | 93 Np | 94 Pu | 95 Am | 96 Cm | 97 Bk | 98 Cf | 99 Es | 100 Fm | 101 Md | 102 No | 103 Lr |