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Nuclides with atomic number of 99 but with different mass numbers
Einsteinium (99 Es) is a
synthetic element , and thus a
standard atomic weight cannot be given. Like all synthetic elements, it has no
stable isotopes . The first
isotope to be discovered (in nuclear
fallout from the
Ivy Mike
H-bomb
test ) was 253 Es in 1952. There are 18 known
radioisotopes from 240 Es to 257 Es, and 5
nuclear isomers . The longest-lived isotope is 252 Es with a
half-life of 471.7 days, or around 1.293 years.
List of isotopes
Nuclide
[n 1]
Z
N
Isotopic mass (
Da )
[2]
[n 2]
[n 3]
Half-life
[1]
Decay mode
[1]
[n 4]
Daughter isotope
Spin and
parity
[1]
[n 5]
[n 6]
Excitation energy
[n 6]
240 Es
99
141
240.06895(39)#
6.0(17) s
α (70%)
236 Bk
4−#
β+ (30%)
240 Cf
β+ ,
SF (0.16%)
(various)
241 Es
[3]
99
142
241.06859(25)#
4.3+2.4 −1.2 s
α
237 Bk
3/2−#
β+ ?
241 Cf
242 Es
[4]
99
143
242.06957(28)#
16.9(8) s
β+
242 Cf
2+#
α (41%)
238 Bk
β+ , SF (1.5%)
(various)
243 Es
99
144
243.06951(22)#
22.1(14) s
α (61%)
239 Bk
(7/2+)
β+ (39%)
243 Cf
244 Es
99
145
244.07088(20)#
37(4) s
β+ (95%)
244 Cf
6+#
α (5%)
240 Bk
β+ , SF (0.011%)
(various)
245 Es
99
146
245.07119(18)#
1.11(6) min
β+ (51%)
245 Cf
(3/2−)
α (49%)
241 Bk
245m1 Es
30(15)# keV
>50# us
IT ?
245 Es
7/2+#
α?
241 Bk
β+ ?
245 Cf
245m2 Es
283(15)# keV
IT
245 Es
(7/2−)
246 Es
99
147
246.072806(97)
7.5(5) min
β+ (90.1%)
246 Cf
4−#
α (9.9%)
242 Bk
β+ , SF (.003%)
(various)
247 Es
99
148
247.073622(21)
4.55(26) min
β+ (93%)
247 Cf
(7/2+)
α (7%)
243 Bk
SF?
(various)
248 Es
99
149
248.075469(56)#
24(3) min
β+ (99.75%)
248 Cf
2−#
α (.25%)
244 Bk
β+ , SF (3.5×10−4 %)
(various)
249 Es
99
150
249.076409(32)#
102.2(6) min
β+ (99.43%)
249 Cf
7/2+
α (.57%)
245 Bk
250 Es
99
151
250.07861(11)#
8.6(1) h
β+
250 Cf
6(+)
α?
246 Bk
250m Es
200(150)# keV
2.22(5) h
β+
250 Cf
1(−)
α?
246 Bk
251 Es
99
152
251.0799914(57)
33(1) h
EC (99.5%)
251 Cf
3/2−
α (.5%)
247 Bk
252 Es
99
153
252.082979(54)
471.7(19) d
α (78(2)%)
248 Bk
(4+)
EC (22(2)%)
252 Cf
253 Es
[n 7]
99
154
253.0848212(13)
20.47(3) d
α
249 Bk
7/2+
SF (8.7×10−6 %)
(various)
254 Es
99
155
254.0880243(32)
275.7(5) d
α
250 Bk
7+
β− (1.74×10−4 %)
254 Fm
SF (<3×10−6 %)
(various)
EC?
254 Cf
254m Es
80.4(11) keV
39.3(2) h
β− (98(2)%)
254 Fm
2+
IT (<3%)
254 Es
α (0.32(1)%)
250 Bk
EC (0.076(7)%)
254 Cf
SF (<0.045%)
(various)
255 Es
99
156
255.090274(12)
39.8(12) d
β− (92.0%)
255 Fm
(7/2+)
α (8.0%)
251 Bk
SF (.0041%)
(various)
256 Es
99
157
256.09360(11)#
7.6 h
β−
256 Fm
7+#
β− , SF (.002%)
(various)
256m Es
0(100)# keV
25.4(12) min
β−
256 Fm
0+#
257 Es
99
158
257.09598(44)#
7.7(2) d
β−
257 Fm
7/2+#
α?
253 Bk
This table header & footer:
^ m Es – Excited
nuclear isomer .
^ ( ) – Uncertainty (1σ ) is given in concise form in parentheses after the corresponding last digits.
^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
^
Modes of decay:
^ ( ) spin value – Indicates spin with weak assignment arguments.
^
a
b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
^ Most common isotope
References
^
a
b
c
d Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021).
"The NUBASE2020 evaluation of nuclear properties" (PDF) . Chinese Physics C . 45 (3): 030001.
doi :
10.1088/1674-1137/abddae .
^ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C . 45 (3): 030003.
doi :
10.1088/1674-1137/abddaf .
^ Khuyagbaatar, J.; Albers, H. M.; Block, M.; Brand, H.; Cantemir, R. A.; Di Nitto, A.; Düllmann, Ch. E.; Götz, M.; Götz, S.; Heßberger, F. P.; Jäger, E.; Kindler, B.; Kratz, J. V.; Krier, J.; Kurz, N.; Lommel, B.; Lens, L.; Mistry, A.; Schausten, B.; Uusitalo, J.; Yakushev, A. (1 October 2020).
"Search for Electron-Capture Delayed Fission in the New Isotope 244 Md" . Physical Review Letters . 125 (14): 142504.
Bibcode :
2020PhRvL.125n2504K .
doi :
10.1103/PhysRevLett.125.142504 .
PMID
33064498 .
S2CID
223546973 .
^ Khuyagbaatar, J.; Cantemir, R. A.; Düllmann, Ch. E.; Jäger, E.; Kindler, B.; Krier, J.; Kurz, N.; Lommel, B.; Schausten, B.; Yakushev, A. (2024-03-18). "Decay properties of the neutron-deficient isotope Es 242". Physical Review C . 109 (3).
doi :
10.1103/PhysRevC.109.034311 .
ISSN
2469-9985 .
Isotope masses from:
Half-life, spin, and isomer data selected from the following sources.
Audi, Georges; Bersillon, Olivier; Blachot, Jean;
Wapstra, Aaldert Hendrik (2003),
"The NUBASE evaluation of nuclear and decay properties" , Nuclear Physics A , 729 : 3–128,
Bibcode :
2003NuPhA.729....3A ,
doi :
10.1016/j.nuclphysa.2003.11.001
National Nuclear Data Center .
"NuDat 2.x database" .
Brookhaven National Laboratory .
Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.).
CRC Handbook of Chemistry and Physics (85th ed.).
Boca Raton, Florida :
CRC Press .
ISBN
978-0-8493-0485-9 .
Group
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Period
Hydrogen and alkali metals
Alkaline earth metals
Pnictogens
Chalcogens
Halogens
Noble gases
①
1
2
②
3
4
5
6
7
8
9
10
③
11
12
13
14
15
16
17
18
④
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
⑤
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
⑥
55
56
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
⑦
87
88
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
⑧
119
120
57
58
59
60
61
62
63
64
65
66
67
68
69
70
89
90
91
92
93
94
95
96
97
98
99
100
101
102