Isotopes of lawrencium

Lawrencium (Lr) has no stable isotopes due to its radioactivity. A standard atomic mass cannot be given, though the atomic mass of the most stable isotope is approx. 262.11.

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
251Lr	103	148	251.09436(32)#	150# µs
252Lr	103	149	252.09537(27)#	390(90) ms [0.36(+11-7) s]
253Lr	103	150	253.09521(24)#	580(70) ms [0.57(+7-6) s]	(7/2-)
253mLr	30(100)# keV			1.5(3) s [1.5(+3-2) s]	(1/2-)
254Lr	103	151	254.09645(36)#	13(3) s
255Lr	103	152	255.09668(22)#	22(4) s	7/2-#
256Lr	103	153	256.09863(24)#	27(3) s
257Lr	103	154	257.09956(22)#	646(25) ms	9/2+#
258Lr	103	155	258.10181(11)#	4.1(3) s
259Lr	103	156	259.10290(8)#	6.2(3) s	9/2+#
260Lr	103	157	260.10550(12)#	2.7 min
261Lr	103	158	261.10688(22)#	44 min
262Lr	103	159	262.10963(22)#	216 min
263Lr	103	160	263.11129(39)#	5# h
264Lr	103	161	264.11404(47)#	10# h
265Lr	103	162	265.11584(77)#	10# h
266Lr	103	163	266.11931(70)#	1# h

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

• 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.