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Isotopes of neptunium



Neptunium (Np) has no stable isotopes. A standard atomic mass cannot be given.

Additional recommended knowledge

19 neptunium radioisotopes have been characterized, with the most stable being 237Np with a half-life of 2.14 million years, 236Np with a half-life of 154,000 years, and 235Np with a half-life of 396.1 days. All of the remaining radioactive isotopes have half-lifes that are less than 4.5 days, and the majority of these have half lifes that are less than 50 minutes. This element also has 4 meta states, with the most stable being 236mNp (t½ 22.5 hours).

Older names for neptunium:

The isotopes of neptunium range in atomic weight from 225.0339 u (225Np) to 244.068 u (244Np). The primary decay mode before the most stable isotope, 237Np, is electron capture (with a good deal of alpha emission), and the primary mode after is beta emission. The primary decay products before 237Np are element 92 (uranium) isotopes (alpha emission produces element 91, protactinium, however) and the primary products after are element 94 (plutonium) isotopes.

237Np is both fissionable and fissile[1]. 237Np eventually decays to form bismuth, unlike most other common heavy nuclei which decay to make lead.

Table

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
excitation energy
225Np 93 132 225.03391(8) 3# ms [>2 µs] 9/2-#
226Np 93 133 226.03515(10)# 35(10) ms
227Np 93 134 227.03496(8) 510(60) ms 5/2-#
228Np 93 135 228.03618(21)# 61.4(14) s
229Np 93 136 229.03626(9) 4.0(2) min 5/2+#
230Np 93 137 230.03783(6) 4.6(3) min
231Np 93 138 231.03825(5) 48.8(2) min (5/2)(+#)
232Np 93 139 232.04011(11)# 14.7(3) min (4+)
233Np 93 140 233.04074(5) 36.2(1) min (5/2+)
234Np 93 141 234.042895(9) 4.4(1) d (0+)
235Np 93 142 235.0440633(21) 396.1(12) d 5/2+
236Np 93 143 236.04657(5) 154(6)E+3 a (6-)
236mNp 60(50) keV 22.5(4) h 1
237Np 93 144 237.0481734(20) 2.144(7)E+6 a 5/2+
238Np 93 145 238.0509464(20) 2.117(2) d 2+
238mNp 2300(200)# keV 112(39) ns
239Np 93 146 239.0529390(22) 2.356(3) d 5/2+
240Np 93 147 240.056162(16) 61.9(2) min (5+)
240mNp 20(15) keV 7.22(2) min 1(+)
241Np 93 148 241.05825(8) 13.9(2) min (5/2+)
242Np 93 149 242.06164(21) 2.2(2) min (1+)
242mNp 0(50)# keV 5.5(1) min 6+#
243Np 93 150 243.06428(3)# 1.85(15) min (5/2-)
244Np 93 151 244.06785(32)# 2.29(16) min (7-)

Notes

  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References

  1. ^ Weiss, P. (October 26, 2002). Little-studied metal goes critical - Neptunium Nukes?. Science News. Retrieved on 2006-09-29.
  • 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).
  • Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure Appl. Chem. Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).
  • 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, Nuc. Phys. A 729, pp. 3-128 (2003).
    • National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (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.


Isotopes of uranium Isotopes of neptunium Isotopes of plutonium
Index to isotope pages
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Isotopes_of_neptunium". A list of authors is available in Wikipedia.
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