Oganesson

Oganesson
118Og
Rn ↑ Og ↓ Usb Extended periodic table tennessine ← oganesson → ununennium
Appearance
unknown
General properties
Name, symbol, number	oganesson, Og, 118
Pronunciation	/ˌɒɡəˈnɛsɒn/ /ˌoʊɡəˈnɛsən/
Element category	Noble gases (predicted)
Group, period, block	18, 7, p
Mass number	294
Electron configuration	[Rn] 5f14 6d10 7s2 7p6 2, 8, 18, 32, 32, 18, 8
History
Discovery	Yuri Oganessian (2002)
Physical properties
see Wikipedia
Atomic properties
see Wikipedia
Most stable isotopes
Main article: Isotopes of oganesson
iso NA half-life DM DE (MeV) DP 294Og syn 0.69 ms α 290Lv
v • t • e • r

Decay chain of ²⁹⁴Og, the only known isotope of oganesson.

Oganesson (Og) is the name of element 118. 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.

No isotopes of Og have predicted half-lives greater than a second, and no isotopes are predicted to be daughters of long-lived nuclides.

A large number of Og isotopes can form during a neutron star merger or comparable event, but all of these are heavier than ³²⁹Og. Supernovae are unlikely to be able to form this element. No isotope which can be synthesized by any technology currently imaginable can form except by physicist-catalyzed reactions.

Any Og which does form will disappear within 316 sec of the event which led to its formation, while its temperature exceeds 10⁶ K. This means quantities such as its group, block, electron configuration, oxidation states, radius (any), crystal structure, melting point, and boiling point do not refer to something which actually exists in this universe (except for one special case; see Note a.)

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. 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. 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 .

Japan Atomic Energy Agency (JAEA) maintains an on-line chart of nuclides which includes decay properties of many predicted nuclides - 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 ³⁷⁹Og decay predominantly by beta emission with half-lives in the 0.001 - 1 sec range. Half-lives aren't reported, but the properties of beta decay indicate that half-lives close to 0.001 sec are likely. Odd-N drops in this band decay by neutron emission.

All isotopes in the band ³⁷⁸Og to ³⁶⁸Og are predicted to have half-lives in the 0.001 - 1 sec range. Dominant decay modes are a mixture of fission and beta emission. Which mode dominates depends on N, with specific values of N associated with fission over a range of Z values. It is likely that both modes are significant for all isotopes.

Isotopes in the band ³⁶⁷Og to ³³⁶Og are predicted to decay by beta emission. All have half-lives in the 0.001 - 1 sec range.

³³⁵Og to ³²⁹Og are predicted to decay by fission and to have half-lives below 0.001 sec. Light isotopes in this band are predicted to have very short half-lives.

predicts a gap from ³²⁸Og to ³¹²Og, which is predicted to be occupied by nuclear drops or very short-lived nuclides.

reports isotopes with half-lives above 10^-6 sec in the band ³¹⁵Og - ³¹³Og. All of these have half-lives in the 0.001 - 1 sec band. They are all predicted to decay by fission. shows no sign of this relatively stable zone.

Both references predict short-lived, fission-decaying isotopes in the band ³¹²Og to ³¹⁰Og.

Between ³⁰⁹Og and ³⁰⁴Og, predicts half-lives in the 10^-6 - 0.001 sec range, while predicts shorter half-lives. In addition, predicts that a transition from fission to alpha emission occurs between ³⁰⁸Og and ³⁰⁷Og, while predicts it to occur between ³⁰⁵Og and ³⁰⁴Og.

While it is invisible in and , shows a dip in half-lives in the band ³⁰⁶Og to ³⁰⁴Og. This is expected for isotopes lying just above the closed shell at N = 184.

Below ³⁰⁴Og, there have been many studies of decay properties. Comparison of these is out of scope for this article. It is worth noting, though, that predicts that ³⁰¹Og, ²⁹⁹Og, and ²⁹⁷Og will all have half-lives close to 0.1 sec and that all other isotopes have shorter half-lives.

The observed half-life of ²⁹⁴Og is shorter than the predicted half-life of any isotope between ²⁹⁶Og and ²⁹²Og. In addition, if the reported half-life of ²⁹⁵Og, 0.12 sec, turns out to be correct, it will be longer than 's prediction of 0.07 sec.

The lightest isotope reported by any of , or is ²⁸¹Og. There may be a few lighter nuclides with half-lives in the 10^-14 - 10^-9 sec range, but half-lives will quickly decline below the minimum needed for a nuclear drop to qualify as a nuclide.

Occurrence

Formation

All even-N nuclear drops from the neutron dripline to ³⁸⁷Og are predicted to be nuclides. Some of these isotopes can form directly as a neutron star disintegrates. Most of them however require a chain of beta decays to form. In the band ³⁸⁶Og to ³⁶⁸Og, some beta decay chains pass through or terminate at Og, but most are truncated by fission at Z < 118. A third band exists from ³⁶⁷Og to ³³⁶Og, containing beta-decaying Og isotopes which can form via beta decay from the neutron dripline. Below that is a fourth band extending from ³³⁷Og to ²⁹³Og in which beta decay chains from the neutron dripline are truncated by fission at Z < 118. Lighter isotopes cannot form since beta decay chains are truncated at Z < 118.

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 Og isotopes.

Persistence

³²⁸Og and heavier isotopes which can form will vanish within 1000 sec after a supernova or neutron star merger which led to their formation.

³²⁷Og through ³¹²Og lie at a higher Z than the terminating nuclides of short-lived beta-decay chains in this mass range.

³¹¹Og and lighter isotopes are predicted to have short half-lives and to be incapable of forming via beta decay from the dripline.

Atomic properties

If the threshold for extinction is set at a molar concentration of 1.5E-30 - which equals [²¹⁸At] in the earth as a whole - all isotopes of Og have become extinct within 10^2.5 (316) sec after the event which led to their formation. At this point Og atoms will be at a temperature on the order of 1.5E06 K, which is equivalent to a mean KE of 136 eV/atom. Based on predicted ionization energies and energy eigenstates, Og will exist only as positive ions, with Og⁺⁹ (loss of all 7s, 7p_1/2, and 7p_3/2 electrons) likely to be its minimum charge. It may exist - briefly - as bare nuclei, but only at emperatures above 10⁹ K.

Oganesson has no chemical properties. It is never cool enough to participate in the multiple-charge-center / bound-electron phenomena we call chemistry^(a).

Notes

a.) Except for one special case: a low-mass, population I (metal-rich) star, with a planet large enough to have an atmosphere and in an orbit which makes liquid water present in contact with both atmosphere and sunlight, several billion years to allow physicists and chemists to evolve, and a cultural willing-ness to spend vast sums of money to study Oganesson.

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