镎只痕量存在于自然界，通常由人工合成制得，因此无法确定标准原子量。镎有从219Np至244Np（不包括221Np）共25种同位素，没有一个是稳定的。最长寿的放射性同位素是237Np，半衰期214.4万年。[1]
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| 符号
|
Z
|
N
|
同位素质量（u）
[n 1][n 2]
|
半衰期
[n 1][n 2]
|
衰变
方式[2]
|
衰变
产物
[n 3]
|
原子核
自旋[n 1]
|
相对丰度
（莫耳分率）
|
| 激发能量[n 1][n 2]
|
225
Np
|
93
|
132
|
225.03391(8)
|
3# ms [>2 µs]
|
α
|
221Pa
|
9/2−#
|
|
226
Np
|
93
|
133
|
226.03515(10)#
|
35(10) ms
|
α
|
222Pa
|
|
|
227
Np
|
93
|
134
|
227.03496(8)
|
510(60) ms
|
α (99.95%)
|
223Pa
|
5/2−#
|
|
| β+ (.05%)
|
227U
|
228
Np
|
93
|
135
|
228.03618(21)#
|
61.4(14) s
|
β+ (59%)
|
228U
|
|
|
| α (41%)
|
224Pa
|
| β+, SF (.012%)
|
(various)
|
229
Np
|
93
|
136
|
229.03626(9)
|
4.0(2) min
|
α (51%)
|
225Pa
|
5/2+#
|
|
| β+ (49%)
|
229U
|
230
Np
|
93
|
137
|
230.03783(6)
|
4.6(3) min
|
β+ (97%)
|
230U
|
|
|
| α (3%)
|
226Pa
|
231
Np
|
93
|
138
|
231.03825(5)
|
48.8(2) min
|
β+ (98%)
|
231U
|
(5/2)(+#)
|
|
| α (2%)
|
227Pa
|
232
Np
|
93
|
139
|
232.04011(11)#
|
14.7(3) min
|
β+ (99.99%)
|
232U
|
(4+)
|
|
| α (.003%)
|
228Pa
|
233
Np
|
93
|
140
|
233.04074(5)
|
36.2(1) min
|
β+ (99.99%)
|
233U
|
(5/2+)
|
|
| α (.001%)
|
229Pa
|
234
Np
|
93
|
141
|
234.042895(9)
|
4.4(1) d
|
β+
|
234U
|
(0+)
|
|
235
Np
|
93
|
142
|
235.0440633(21)
|
396.1(12) d
|
ε
|
235U
|
5/2+
|
|
| α (.0026%)
|
231Pa
|
236
Np
[n 4]
|
93
|
143
|
236.04657(5)
|
1.54(6)×105 y
|
ε (87.3%)
|
236U
|
(6−)
|
|
| β− (12.5%)
|
236Pu
|
| α (.16%)
|
232Pa
|
236m
Np
|
60(50) keV
|
22.5(4) h
|
ε (52%)
|
236U
|
1
|
|
| β− (48%)
|
236Pu
|
237
Np
[n 4][n 5]
|
93
|
144
|
237.0481734(20)
|
2.144(7)×106 y
|
α
|
233Pa
|
5/2+
|
痕量[n 6]
|
| SF (2×10−10%)
|
(various)
|
| CD (4×10−12%)
|
207Tl
30Mg
|
238
Np
|
93
|
145
|
238.0509464(20)
|
2.117(2) d
|
β−
|
238Pu
|
2+
|
|
238m
Np
|
2300(200)# keV
|
112(39) ns
|
|
|
|
|
239
Np
|
93
|
146
|
239.0529390(22)
|
2.356(3) d
|
β−
|
239Pu
|
5/2+
|
痕量[n 6]
|
240
Np
|
93
|
147
|
240.056162(16)
|
61.9(2) min
|
β−
|
240Pu
|
(5+)
|
痕量[n 7]
|
240m
Np
|
20(15) keV
|
7.22(2) min
|
β− (99.89%)
|
240Pu
|
1(+)
|
|
| IT (.11%)
|
240Np
|
241
Np
|
93
|
148
|
241.05825(8)
|
13.9(2) min
|
β−
|
241Pu
|
(5/2+)
|
|
242
Np
|
93
|
149
|
242.06164(21)
|
2.2(2) min
|
β−
|
242Pu
|
(1+)
|
|
242m
Np
|
0(50)# keV
|
5.5(1) min
|
|
|
6+#
|
|
243
Np
|
93
|
150
|
243.06428(3)#
|
1.85(15) min
|
β−
|
243Pu
|
(5/2−)
|
|
244
Np
|
93
|
151
|
244.06785(32)#
|
2.29(16) min
|
β−
|
244Pu
|
(7−)
|
|
Close
画上#号的数据代表没有经过实验的证明，仅为理论推测。
- Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
- Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
- Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties （页面存档备份，存于互联网档案馆）, Nuc. Phys. A 729, pp. 3-128 (2003).
- National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database （页面存档备份，存于互联网档案馆） (retrieved Sept. 2005).
- David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.
