Einsteinium

Einsteinium, Es, is the name of element 99. Wikipedia has an article which provides a lot of information about the element.  This article will focus on things Wikipedia does not stress: formation and the element's natural presence on earth..

Es has the highest atomic number of any element whose entire valley of beta stability has been experimentally studied.

Neither of its two longest-lived isotopes, ²⁵⁴Es and ²⁵²Es can form in quantity via rapid neutron capture followed by beta decay. The longest-lived isotopes which can form are ²⁵⁵Es, at roughly 40 days, ²⁵³Es at 20 days. and both ²⁵⁷Es and ²⁵⁹Es (predicted) near 8 days. When Es is produced in a supernova or neutron star merger, it survives long enough to become a part of the remnant, but not for long. It may persist long enough to be incorporated into dust.

In rocky bodies chemically active enough to concentrate uranium, ²⁵³Es is produced by beta decay of ²⁵³Cf. With its 17.8 day half-life, and 0.99 beta decay branch ratio, that nuclide switches the main path by which nuclides grow from Cf to Es. Subsequent slow neutron capture can reach ²⁵⁶Es. Since the process is driven by spontaneous fission of U, it continues wherever U is concentrated enough. Es is a terrestrial element, produced on earth today without the benefit of scientists.

Nuclear properties

If transmuting from nuclide (Z₁,A₁) into (Z₂,A₂) releases energy, there is some chance that the transmutation will occur. In some cases, the transmutation is likely, in others, it is rare. With large nuclides, there are usually four kinds of transmutation available. If they are neutron-rich, neutrons are heavier than protons. Turning a neutron into a proton releases energy, so these nuclides will beta-decay, releasing energy in the form of an electron and an antineutrino. If they are proton rich, they have three main choices, The first is positive beta decay Turning a proton into a neutron reduces electrical potential energy enough to pay the mass-energy debt the transformation requires. There are two ways to do this, positron emission and electron capture. In both cases, beta (b-) and positive beta (b+) decay half-lives increase as energy yield declines. Heavy isotopes of any Z try to decay by (b-) emission. As A goes down, half-lives increase until the reaction becomes impossible. Then, after a gap of at least one isotope, (b+) decay sets in and becomes increasingly short-lived in the lightest isotopes.

Es has the highest atomic number of any element for which the entire band - from the lightest b- decaying to heaviest b+ decaying isotopes - has been observed. The heaviest Es isotopes observed decay by beta emission.

Information sources

Japan Atomic Energy Agency (JAEA) maintains an on-line chart of nuclides which includes decay properties of many predicted nuclides⁽¹⁾ - 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. This reference provides the most focused look at the most significant predicted Es isotopes. Other references used are cited.

Predicted and observed properties

Isotopes from the neutron dripline down to ²⁵⁸Es are predicted to decay primarily by beta emission. Half lives increase, as A declines, from around 0.001 sec at the dripline to 100 sec at ²⁶³Es and peaking at 7 days in ²⁵⁹Es.

Among observed isotopes, beta decay continues as far as ²⁵²Es.

Fission is predicted to occur between ²⁶³Es and ²⁵⁸Es, but branch ratios are small. This is consistent with the weak fission branches observed at ²⁵⁵Es through Es²⁵³.

Isotopes of Es as light as ²⁴⁰Es have been observed. Additional isotopes down to ²³⁰Es are predicted in Ref. 1.

Ref. 3 predicts that an additional isotope, ²²⁸Es, will have a half-life exceeding 10^-9 sec. All are short lived, with half-lives under 0.001 sec. These isotopes are predicted to decay by fission, alpha emission or proton emission. These are stabilized by the N = 126 neutron shell closure.

Occurence

Formation

a) Outside Earth

It appears likely that Es isotopes from the neutron dripline down to ²⁵⁹Es can form. While fission may occur in some beta decay chains, there is little risk that any isotope with Z < 99 and A > 258 will have no beta-decay branch.

The odd-N isotopes ²⁵⁷Es, ²⁵⁵Es, and ²⁵³Es can form. Even-N isotopes ²⁵⁸Es, ²⁵⁶Es, ²⁵⁴Es, and ²⁵²Es cannot form via rapid neutron capture and beta decay chains. They are blocked by Cf isotopes which have no observed beta decay branch.

²⁵¹Es and lighter isotopes are blocked from forming via rapid neutron capture & beta decay⁽⁴⁾.

While Es is produced in some quantity in neutron star mergers and supernovae, those nuclides will decay quickly. After a short time, the only Es remaining in a body will be what is produced continuously by slow neutron capture. Spontaneous fission of ²³⁸U produces free neutrons. This small flux of neutrons will produce a small amount of isotopes in the ²⁵⁵Es to ²⁵³Es band. Concentration of Es will be many orders of magnitude smaller than uranium concentration; so only geologically-active rocky bodies like the earth, which can concentrate uranium, will contain potentially-detectable quantities of Es.

b) On Earth

While Es is produced in some quantity in neutron star mergers and supernovae, those nuclides will decay quickly. After a short time, the only Es remaining in a body will be what is produced continuously by slow neutron capture. Spontaneous fission of ²³⁸U produces free neutrons. This small flux of neutrons will produce a small amount of isotopes in the ²⁵⁵Es to ²⁵³Es band. Concentration of Es will be many orders of magnitude smaller than uranium concentration; so only geologically-active rocky bodies like the earth, which can concentrate uranium, will contain potentially-detectable quantities of Es.

Persistence

The amount of Es produced during a supernova, neutron star merger, or comparable event will only be a few orders of magnitude less than the amount of uranium produced. Most of it decays until it either vanishes or comes into equilibrium with the continuous, slow production resulting from ²³⁸U fission.

Neither of the two longest-lived Es isotopes, ²⁵⁴Es and ²⁵¹Es can form via rapid neutron capture and beta decay. Of those which can form, ²⁵⁵Es may persist, in principle, as long as 20 yrs, although it will be detectable for a much shorter time.

²⁵⁴Es can form via terrestrial-type slow neutron capture, so it (and other Es isotopes formed in this way) will persist as long as ²³⁸U does.

Atomic properties

Wikipedia's article "Einsteinium" addresses the element's atomic properties and chemistry in some detail.

References

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

2. "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".

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

4. "Isotopes of Einsteinium", 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

(11-21-20)