Bohrium

Not to be confused with Boron or Barium.

Bohrium, Bh, is the name of element 107. Wikipedia has an article which provides a lot of information about the element.  This article will focus on things Wikipedia does not stress: heavy isotopes and formation.

The isotopes ²⁸¹Bh, ²⁸³Bh and all isotopes heavier than ²⁸³Bh can form (although fission will reduce the amount which forms in the vicinity of ²⁹⁵Hs). It is unlikely that ²⁸²Bh and the isotopes ²⁸⁰Bh and lighter can form due to fission-decaying isotopes of Sg. The longest-lived isotope is expected to be ²⁸¹Bh, at perhaps as much as 3 hr. It will persist less than a year after an event which forms it. ²⁸³Bh is expected to have the second-longest half-life at about 1/2 hr. No isotope of Bh is expected to persist long enough to be a significant component of kilonova or supernova remnants.

NUCLEAR PROPERTIES

INFORMATION SOURCES

This article uses two main resources chosen because of their independence from one another. A third source provides quantitative data over a limited range.

At least one document maps half-life and decay mode for elements below Z = 175 from the neutron dripline down to isotopes which are too neutron-poor to survive any appreciable length of time⁽¹⁾. Maps on pp 15 & 18 address the entire (Z,N) region covered, but report only the dominant decay mode and report half-lives only to within a band three orders of magnitude wide (0.001 - 1 sec, for example). More detailed estimates of these properties can be extracted from maps on pp 11 & 12, but only for a limited range of Z and N. Half-life data are reported by colors, which makes numerical estimates laborious to produce. This document is connected to Japan's KTUY model.

An independent map of half-lives and decay modes exists⁽²⁾. This one is limited to A = 339, as well as to Z = 132. It does not show short-lived isotopes well, and gives half-lives only within rather broad and awkward bands. It does show multiple decay modes for single nuclides. It originates from models used by the Russian agency JINR, so is completely independent of Ref. 1.

Japan Atomic Energy Agency (JAEA) maintains an on-line chart of nuclides which includes decay properties of many predicted nuclides⁽³⁾ - unlike charts published by Korea Atomic Energy Research Institute (KAERI) or the (U.S.) National Nuclear Data Center (NNDC). This chart gives separate numerical values for partial half-lives against fission, beta emission (both b^- and b⁺), and alpha emission. These appear to be systematically too long, but are probably reliable to within an order of magnitude in most cases.

The U.S.'s Los Alamos National Laboratory (LANL) contains tabulated partial half-life data for alpha and beta decay⁽⁴⁾. If it included fission, it would be a primary resource for this article, but it does not. Where fission is not an issue, though, it constitutes a third independent source of decay properties.

PREDICTED PROPERTIES

Isotopes from the neutron dripline down to 301Bh are predicted to decay primarily by beta emission, usually with half-lives in the 0.001 - 1 sec range. Isotopes at the light end of this band are likely to decay by a mixture of beta emission and fission.

Between ³⁰⁰Bh and ²⁹⁴Bh, Ref. 1 predicts that fission will be the dominant mode for decay; but it also predicts half-lives over 0.001 sec in all but one case, which is long enough that beta decay will probably be an important secondary decay mode. The exception, ²⁹⁵Bh, is predicted to have a half-life in the 10^-06 - 0.001 sec range, so that some beta decay is likely to occur. Ref. 2 predicts decay by fission throughout the band ³⁰²Bh to ²⁹³Bh. It predicts lower stability, and half lives under 10^-06 sec for ²⁹⁸Bh and ²⁹⁷Bh. Ref. 2 predicts that little beta decay is possible in this band.

It is likely that beta decay will predominate in ²⁹³Bh and ²⁸²Bh, and that half-lives of all isotopes in this band will exceed 1 sec, but are unlikely to exceed 1000 sec. The sources are not fully in agreement in all cases, but consensus generally exists.

It is likely that both ²⁸¹Bh and ²⁸⁰Bh will decay by fission. Refs 1 and 3 agree on this point, and Ref. 2's assignment of beta emission as the dominant mode of decay seems uncertain. ²⁸¹Bh may have a half-life on the order of 3 days, while ²⁸⁰Bh probably has a half-life under 1000 sec.

Refs 1 through 3 all indicate that ²⁷⁹Bh should decay by fission. Ref. 3 predicts a half-life around 1 sec, which is anomalously low compared to adjacent even-N isotopes ²⁸¹Bh and ²⁷⁷Bh. Ref. 1 predicts a half-life in the vicinity of 100 sec, which is still low, compared to the adjacent even-N isotopes; but less dramatically so. It seems reasonably safe to say that the half-life of ²⁷⁹Bh will be under 1000 sec.

The available sources diverge in their predictions for the decay mode of ²⁷⁸Bh, but show somewhat closer agreement that its predicted half-life will be in the vicinity of 1 hr. However, there is an unconfirmed report of ²⁷⁸Bh observation which gives its decay mode as fission and its half-life as roughly 10 min⁽⁵⁾.

Although there is some divergence between sources, it appears that ²⁷⁷Bh is predicted to decay by a mix of alpha emission and fission with a half-life under 1 hr.

There is an agreement among the sources used that ²⁷⁶Bh and ²⁷⁵Bh will decay by fission with half lives under 1 sec.

Ref. 3 predicts that the unobserved isotope ²⁷³Bh will decay by fission with a half-life around 0.02 sec. This is consistent with predictions of rising fission partial half-lives in the vicinity of N = 162 and falling alpha partial half-lives with declining A in this region. It is also consistent with the decay properties observed for ²⁷¹Bh.

Ref. 3 also predicts that ²⁶⁹Bh and ²⁶⁸Bh will have a dominant alpha-decay branch and that both of them will have half-lives under 1 sec.

Investigation of the decay properties of undiscovered isotopes lighter than ²⁶⁸Bh is out of scope for this article.

The lightest isotope reported in the vicinity of N = 184 by any of Refs. 1 through 3 is ²⁵³Bh. There may be a few lighter nuclides with half-lives in the 10^-14 - 10^-09 sec range in this region, but half-lives will quickly decline below the minimum needed for a nuclear drop to qualify as a nuclide.

Ref. 1 predicts that no isotopes of Bh in the vicinity of the N = 126 shell closure will have half-lives over 10^-09 sec.

OCCURRENCE

FORMATION

Bh isotopes from the neutron dripline to ²⁸³Bh can form. Heavier isotopes can form directly, but the isotopes of greatest interest require a beta decay chain in order to form. Fission-decaying nuclides with Z < 107 with near A = 295 can be expected to reduce the quantity of material which reaches Bh, but is not expected to completely block the decay chains.

Half-lives of beta-decaying isotopes should increase as A declines. Half-lives exceeding a few seconds are unlikely above A = 290, and half-lives of isotopes in the ²⁸⁹Bh to ²⁸³Bh band can be expected to lie in the range of 1 sec - 1 hr. The amounts of ²⁸⁴Bh which forms may be limited by fission at ²⁸⁴Sg.

It is not certain whether ²⁸²Bh can form. ²⁸²Sg is expected to have a long partial half-life against beta emission and a short partial half-life against fission. If possible at all, only limited amounts of ²⁸²Bh can form. Its half-life is expected to be a few minutes.

It is likely that ²⁸¹Bh can form. It is expected to primarily by fission, but with a significant beta-decay branch. Its half-life is expected to be up to around 5 hr. It is likely to be the longest-lived isotope of Bh which can form.

There appears to be fairly good consensus that ²⁸⁰Sg through ²⁷²Sg will decay only by fission. This would prevent ²⁸⁰Bh and lighter isotopes from forming.

Both high-A nuclides ejected from a disintegrating neutron star and high-A nuclides produced by rapid neutron capture contribute to the production of Bh. Both supernovae and neutron star mergers are expected to produce the element.

PERSISTENCE

²⁸¹Bh may persist for as much as a year after a supernova, neutron star merger, or other event which led to its formation. Other isotopes are expected to persist for shorter times.

ATOMIC PROPERTIES

Wikipedia's article "Bohrium" addresses the element's atomic properties and chemistry in some detail. It is unlikely that any Bh can survive, outside the laboratory, to reach an environment cool enough for chemical interactions to occur.

REFERENCES

1. "Decay Modes and a Limit of Existence of Nuclei"; H. Koura; 4th Int. Conf. on the Chemistry and Physics of Transactinide Elements; Sept. 2011.

2. “Systematic Study of Decay Properties of Heaviest Elements.”; Y. M. Palenzuela, L. F. Ruiza, A. Karpov, and W. Greiner; Bulletin of the Russian Academy of Sciences, Physics.  Vol . 76, No.11, pp 1165 – 1177; 2012

3. "Chart of the Nuclides, 2014", Japan Atomic Energy Agency; website available using "chart of nuclides" and "JAEA" as internet search terms.

4. "Nuclear Properties for Astrophysical Applications"; P. Moller & J. R. Nix; Los Alamos National Laboratory website; search by "LANL, T2", then "Nuclear Properties for Astrophysical Applications".

5. "Isotopes of Bohrium", Wikipedia article.

9-Period Periodic Table of Elements
1	1 H																																																																	2 He
2	3 Li	4 Be																																																																	5 B	6 C	7 N	8 O	9 F	10 Ne
3	11 Na	12 Mg																																																																	13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
4	19 K	20 Ca																																																																	21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
5	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
6	55 Cs	56 Ba																																																					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	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
7	87 Fr	88 Ra																																																					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	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
8	119 Uue	120 Ubn																															121 Ubu	122 Ubb	123 Ubt	124 Ubq	125 Ubp	126 Ubh	127 Ubs	128 Ubo	129 Ube	130 Utn	131 Utu	132 Utb	133 Utt	134 Utq	135 Utp	136 Uth	137 Uts	138 Uto	139 Ute	140 Uqn	141 Uqu	142 Uqb	143 Uqt	144 Uqq	145 Uqp	146 Uqh	147 Uqs	148 Uqo	149 Uqe	150 Upn	151 Upu	152 Upb	153 Upt	154 Upq	155 Upp	156 Uph	157 Ups	158 Upo	159 Upe	160 Uhn	161 Uhu	162 Uhb	163 Uht	164 Uhq	165 Uhp	166 Uhh	167 Uhs	168 Uho	169 Uhe	170 Usn	171 Usu	172 Usb
9	173 Ust	174 Usq
Alkali metal Alkaline earth metal Lanthanide Actinide Superactinide Transition metal Post-transition metal Metalloid Other nonmetal Halogen Noble gas predicted predicted predicted predicted predicted predicted predicted predicted predicted

(11-02-20)