Copernicium

Copernicium (Cn) is the name of element 112. 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 longest lived Cn isotopes are predicted to lie in the band from ²⁹⁶Cn to ²⁹³Cn, all of which have half-lives exceeding 1 year. Peak half-life may be on the order of 1000 years, although much shorter half-lives are likely.

Many isotopes of Cn are expected to form during neutron star mergers, including its longest-lived isotopes. These long-lived isotopes are likely to form during supernovae as well. These may persist for thousands of years.

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.

PREDICTED PROPERTIES

Even-N isotopes from the neutron dripline down to ³⁵⁵Cn are predicted to have half-lives in the 0.001 - 1 sec range. [Half-lives aren't reported directly, but the properties of beta decay indicate that half-lives close to 0.001 sec are likely⁽⁴⁾]. In a few cases, fission is predicted to be the dominant decay mode, but may be a significant secondary mode for other isotopes. Odd-N drops in this band decay by neutron emission.

Isotopes in the band ³⁵⁴Cn to ³¹⁷Cn are predicted to decay by beta emission, with half-lives in the 0.001 - 1 sec range. Some light isotopes in this band may have fission as a secondary decay mode.

Ref. 1 predicts that fission will become the principal decay mode in the ³¹⁶Cn to ³⁰⁹Cn band. Half lives are predicted to exceed 1 sec at the upper end of this band, then fall, reaching the 10^-06 - 0.001 sec range at its low-A end. Ref. 2 indicates half-lives in 10^-06 - 0.001 sec range at the band's heavy end and half-lives below 10^-06 sec at its light end.

Ref 1 predicts a gap from ³⁰⁸C to ³⁰⁴Cn, All isotopes in this band have half-lives under 10^-09 sec, and most may not even survive the 10^-14 sec needed to qualify as nuclides. Ref. 2 predicts all will have half-lives under 10^-06, which is as short a time as that document reports. Fission is the predicted decay mode in both cases.

Both Refs 1 & 2 predict that ³⁰³Cn and ³⁰²Cn will decay by fission with half-lives under 10^^-06 sec.

Both Refs 1 & 2 predict that ³⁰¹Cn and ³⁰⁰Cn will decay by fission, but Ref. 1 predicts half-lives exceeding 1 sec while Ref. 2 predicts half-lives under 0.001 sec.

Ref. 1 predicts that ²⁹⁹Cn will decay principally by beta emission with a half-life exceeding 1 sec, while Ref. 2 predicts fission and a half-life in the 0.001 - 1 sec. range. Both modes are probably significant.

Below ²⁹⁹Cn, there have been many studies of decay properties. There does seem to be consensus that fission will not be a significant decay mode, that half-lives will peak just below ²⁹⁷Cn, and that long half-lives will be possible near N = 184. Ref. 3 predicts that the isotopes ²⁹⁶Cn and ²⁹⁴Cn to ²⁹²Cn will decay exclusively by alpha emission with half-lives of 2.7, 360, 2.9 and 0.1 years respectively. It also predicts that ²⁹⁵Cn will have a half-life of 2.2 years, but decay split almost evenly between alpha and beta (Since it is close to the upper edge of beta stability, it probably decays by (b-) emission alone.) Among the other isotopes, ²⁹¹Cn is predicted to have a half-life on the order of 4.5 days and decays predominantly by (b+ / EC), ²⁹⁰Cn is predicted to have a half-life on the order of 2.5 days and to decay by alpha emission, and the remainder are predicted to have shorter half-lives. Fission is predicted to become the dominant decay mode below ²⁸⁰Cn and half-lives are predicted to become quite short. Further comparison of predicted decay properties or evaluation of likely actual properties is out of scope for this article.

The unconfirmed isotope ²⁸⁶Cn has been reported to decay by fission with a half-life close to 30 sec. Ref. 3 predicts alpha emission and a half-life of close to 1/2 hr. ²⁷⁷Cn, on the other hand, is reported to have a half-life of 0.0011 sec and decay by alpha emission. Adjacent odd-N isotopes both above and below it are predicted to decay predominantly by fission with shorter half-lives.

The lightest isotope reported in the vicinity of N = 184 by any of Refs. 1 through 3 is ²⁶⁸Cn. 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 three isotopes exist in the band ²⁴³Cn to ²⁴⁰Cn. All are predicted to have half-lives in the 10^-09 - 10^-06 sec range and to decay by proton emission. Neutron counts for these isotopes are 131 and 128 respectively, just above N = 126.

OCCURRENCE

FORMATION

Cn isotopes from the neutron dripline to ³⁰⁷Cn can form. Heavier isotopes in this band can form directly as a neutron star disintegrates; largely from dripline nuclides, but also as fission daughters of very large nuclear drops. Lighter isotopes require a chain of beta decays to form, but all lower-Z nuclides in such chains have long enough partial half-lives against fission that attrition will not be severe. The lightest isotopes are themselves short-lived, fission decaying species.

Below ³⁰⁷Cn, it is necessary to examine the possibility of fission attrition cutting off beta-decay chains below Z = 112. The article "Superheavy Island is Deserted" (this wiki) tabulates two sets of data for attenuation by fission and cutoff by nuclides which do not have a beta decay branch. Set 1 is based on Refs. 1 & 3, and Set 2 is based on Ref. 2. Set 1 indicates that ³⁰⁶Cn and ³⁰⁵Cn can form, but only in small quantities, while Set 2 indicates that neither isotope can form. Both data sets indicate that no isotopes in the band ³⁰⁴Cn to ²⁹⁶Cn can form.

Set 1 indicates that fission attrition would allow ²⁹⁵Cn to form, although in minute quantities, but Set 2 indicates that attrition is too great. Whether it can form is uncertain. Set 1 indicates that limited attrition would allow ²⁹⁴Cn to form, but that the beta-decay chain leading to it is interrupted by ²⁹⁴Ds. Set 2, on the other hand, shows ²⁹⁴Ds as a short-lived, beta-decaying nuclide, but shows fission attenuation to be so severe that the isotope cannot form. Either way, it is unlikely that ²⁹⁴Cn can form. Both sets indicate that ²⁹³Cn can form, although fission attrition is severe. Set 1 indicates that the beta-decay chains leading to ²⁹²Cn and ²⁹¹Cn are blocked by the alpha-decaying nuclides ²⁹²Ds and ²⁹¹Rg respectively; while Set 2 indicates that small quantities of both can form. It is uncertain which is accurate. Below ²⁹¹Cn, all of Refs 1, 2, and 3 indicate that beta decay to Cn is blocked at Z < 112, so lighter isotopes cannot form.

Material ejected from a disintegrating neutron star can be expected to cover the entire range of possible Cn isotopes, so will cause production of all isotopes. Several studies of rapid neutron capture (r process) indicate that neutron capture reactions may produce nuclides with A up to around 380 before fission attrition prevents further growth. Neutron capture can contribute to production of but the heaviest Cn isotopes - in particular, long-lived Cn isotopes are produced in supernovae as well as neutron star mergers.

PERSISTENCE

Most Cn isotopes which can form are short lived and have short-lived precursors. They can be expected to disappear within 1000 sec of the event which led to their formation. Only ²⁹³Cn, and possibly ²⁹⁵Cn, ²⁹²Cn, and ²⁹¹Cn may persist for long. At the most optimistic, ²⁹³Cn and ²⁹¹Cn may persist for up to 100000 years, although 6000 years is more realistic. ²⁹⁵Cn and ²⁹²Cn probably don't persist for more than 250 years.

ATOMIC PROPERTIES

Wikipedia's article "Copernicium" addresses the element's atomic properties and chemistry in some detail. Although its formation is uncertain, and the amounts which can form outside the laboratory are tiny, it does appear to be possible that Cn chemistry can exist without the presence of chemists.

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". rnicum", 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
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(10-11-20)