Moscovium

Moscovium
Symbol	Mc
Number	115
Group, Period	15, 7
Mass number	not applicable
Category	Post-transition metal (Predicted)
Electronic properties
Electrons per shell	2, 8, 18, 32, 32, 18, 5 (Predicted)
Discovery information
Discoverer	Joint Institute for Nuclear Research
Date discovered	2 Febuary 2004
Location discovered	Dubna, Russia

Moscovium (Mc) is the name of element 115. 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 Mc isotopes are predicted to lie in the band from ²⁹⁹Mc to ²⁹⁵Mc. Peak half-life is predicted to be near 1/2 hour. Those isotopes cannot form. Longest half-lives for isotopes which can form, all of which are heavier than ³¹⁶Mc, are predicted to be under a second. Any Mc which does form will disappear within 1000 sec of the event which led to its formation. This means that the element will never be in an environment cool enough for it to interact chemically.

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.

PREDICTED PROPERTIES

Even-N isotopes from the neutron dripline down to ³⁶⁸Mc 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 some cases, fission is predicted to be the dominant decay mode, but both fission and beta emission are likely to be significant modes for all isotopes. Odd-N drops in this band decay by neutron emission.

Isotopes in the band ³⁶⁷Mc to ³³³Mc are predicted to decay by beta emission. All are predicted to have half-lives in the 0.001 - 1 sec range.

³³²Mc to ³²⁷Mc is a transition band. Half-lives are all predicted to be in the range 0.001 - 1 s, but the principal decay mode is sometimes beta emission and sometimes fission. Both modes are likely to be important in all isotopes.

Isotopes in the band ³²⁶Mc to ³¹⁹Mc are predicted to decay by fission. All are predicted to have half-lives in the 0.001 - 1 sec range, except for ³¹⁹Mc, which is predicted to have a half-life in the 10^-06 - 0.001 sec range. This may be a minor difference, or may reflect the onset of instability with respect to fission.

Ref 1 predicts a gap from ³¹⁸Mc to ³⁰⁷Mc, All isotopes in this band have half-lives under 10^-06 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.

The band ³⁰⁶Mc to ³⁰²Mc is a transition region which contains significant differences between the predictions of Ref. 1 & 3, and those of Ref. 2. The former predict a rapid rise in half-life as A declines to a peak near 30 sec, followed by an abrupt drop as N approaches 184. This is similar to the pattern observed above N = 126. Principal decay mode shifts to alpha emission at ³⁰⁴Mc, indicating increased stability with respect to fission near N = 184. Ref. 2 predicts increasing half-life throughout the band, as well predicting that fission will dominate throughout the band.

Below ³⁰²Mc, 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 ³⁰⁰Mc, and that even the most stable isotopes will have moderate half lives. Ref. 3 predicts that ²⁹⁹Mc will have a half-life exceeding 1500 sec, and that all of ²⁹⁸Mc to ²⁹⁵Mc will have half-lives exceeding 100 sec. There is disagreement on whether b+ / EC will be an important decay mode. Ref. 2 & 3 indicate that it will be, while Ref. 1 indicates that it will not be. Further comparison of predicted decay properties or evaluation of likely actual properties is out of scope for this article.

Observed half-lives in the band ²⁹⁰Mc to ²⁸⁷Mc are an order of magnitude shorter than half-lives of adjacent isotopes predicted in Ref. 3, both above and below the band.

The lightest isotope reported by any of Refs. 1 through 3 is ²⁷⁷Mc. There may be a few lighter nuclides with half-lives in the 10^-14 - 10^-09 sec range, but half-lives will quickly decline below the minimum needed for a nuclear drop to qualify as a nuclide.

OCCURRENCE

FORMATION

Moscovium isotopes are predicted from the neutron dripline to ³¹⁹Mc. Most are beta emitters, but a few decay mainly by fission. All are short-lived. Between ³¹⁸Mc and ²⁹⁴Mc, beta decay chains are truncated by fission at Z < 115. This band includes the relatively long-lived isotopes stabilized by neutron shell closure at N = 184. Below ²⁹⁴Mc, beta decay chains are interrupted by alpha-decaying nuclides, but the effect is the same; no light isotope of Mc can form. Material ejected from a disintegrating neutron star is expected to cover the entire band of possible nuclides, although quantity may be small at high A.

Neutron capture may be able to produce nuclides up to A around 380 before fission attrition stops further growth. Neutron capture is expected to contribute to formation of all significant Mc isotopes.

PERSISTENCE

All Mc isotopes which can form have short half-lives and are the result of beta decay of short-lived nuclides. The element is expected to disappear completely less than 1000 sec after a neutron star merger of similar event which led to its formation.

ATOMIC PROPERTIES

Wikipedia's article "Moscovium" addresses the element's atomic properties and chemistry in some detail. One point it does not make is that, while Mc nuclei can form, they do not persist long enough to reach an environment cool enough to allow chemical processes. The chemistry of Mc is entirely synthetic.

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".

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

(10-08-20)