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Isotopes of beryllium

Although beryllium (Be) has multiple isotopes, only one of these isotopes is stable; as such, it is considered a monoisotopic element.

Standard atomic mass: 9.012182(3) u

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)
nuclide symbol	excitation energy			half-life	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
⁵Be	4	1	5.04079(429)#		(1/2+)#
⁶Be	4	2	6.019726(6)	5.0(3)E-21 s [0.092(6) MeV]	0+
⁷Be	4	3	7.01692983(11)	53.22(6) d	3/2-
⁸Be	4	4	8.00530510(4)	67(17)E-18 s [6.8(17) eV]	0+
⁹Be	4	5	9.0121822(4)	STABLE	3/2-	1.0000
¹⁰Be	4	6	10.0135338(4)	1.51(6)E+6 a	0+
¹¹Be	4	7	11.021658(7)	13.81(8) s	1/2+
¹²Be	4	8	12.026921(16)	21.49(3) ms	0+
¹³Be	4	9	13.03569(8)
¹⁴Be	4	10	14.04289(14)	4.84(10) ms	0+
¹⁵Be	4	11	15.05346(54)#	<200 ns
¹⁶Be	4	12	16.06192(54)#	<200 ns	0+

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.

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.