Isotopes of zirconium

Naturally occurring zirconium (Zr) is composed of four stable isotopes, and one extremely long-lived radioisotope (⁹⁶Zr), which decays via double beta decay with the observed half-life of 2.0×10¹⁹ years [1]; it can also undergo single beta decay which is not yet observed, but the theoretically predicted value of T_½ is 2.4×10²⁰ years [2]. The second most stable radioisotope is ⁹³Zr which has a half-life of 1.53 million years. Eighteen other radioisotopes have been observed. Most of these have half-lives that are less than a day except for ⁹⁵Zr (64.02 days), ⁸⁸Zr (63.4 days), and ⁸⁹Zr (78.41 hours). The primary decay mode is electron capture for isotopes lighter than ⁹²Zr, and the primary mode for heavier isotopes is beta decay.
Standard atomic mass: 91.224(2) u.

Zircornium is the heaviest element that can be formed from symmetric fusion, from either ⁴⁵Sc, or ⁴⁶Ca producing ⁹⁰Zr and ⁹²Zr respectively. All heavier elements are formed either through asymmetric fusion or during the collapse of supernovae.

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)
⁷⁸Zr	40	38	77.95523(54)#	50# ms [>170 ns]	0+
⁷⁹Zr	40	39	78.94916(43)#	56(30) ms	5/2+#
⁸⁰Zr	40	40	79.9404(16)	4.6(6) s	0+
⁸¹Zr	40	41	80.93721(18)	5.5(4) s	(3/2-)#
⁸²Zr	40	42	81.93109(24)#	32(5) s	0+
⁸³Zr	40	43	82.92865(10)	41.6(24) s	(1/2-)#
⁸⁴Zr	40	44	83.92325(21)#	25.9(7) min	0+
⁸⁵Zr	40	45	84.92147(11)	7.86(4) min	7/2+
^85mZr	292.2(3) keV			10.9(3) s	(1/2-)
⁸⁶Zr	40	46	85.91647(3)	16.5(1) h	0+
⁸⁷Zr	40	47	86.914816(9)	1.68(1) h	(9/2)+
^87mZr	335.84(19) keV			14.0(2) s	(1/2)-
⁸⁸Zr	40	48	87.910227(11)	83.4(3) d	0+
⁸⁹Zr	40	49	88.908890(4)	78.41(12) h	9/2+
^89mZr	587.82(10) keV			4.161(17) min	1/2-
⁹⁰Zr	40	50	89.9047044(25)	STABLE	0+	0.5145(40)
^90m1Zr	2319.000(10) keV			809.2(20) ms	5-
^90m2Zr	3589.419(16) keV			131(4) ns	8+
⁹¹Zr	40	51	90.9056458(25)	STABLE	5/2+	0.1122(5)
^91mZr	3167.3(4) keV			4.35(14) µs	(21/2+)
⁹²Zr	40	52	91.9050408(25)	STABLE	0+	0.1715(8)
⁹³Zr	40	53	92.9064760(25)	1.53(10)E+6 a	5/2+
⁹⁴Zr	40	54	93.9063152(26)	STABLE [>1.1E+17 a]]	0+	0.1738(28)
⁹⁵Zr	40	55	94.9080426(26)	64.032(6) d	5/2+
⁹⁶Zr	40	56	95.9082734(30)	20(4)E+18 a	0+	0.0280(9)
⁹⁷Zr	40	57	96.9109531(30)	16.744(11) h	1/2+
⁹⁸Zr	40	58	97.912735(21)	30.7(4) s	0+
⁹⁹Zr	40	59	98.916512(22)	2.1(1) s	1/2+
¹⁰⁰Zr	40	60	99.91776(4)	7.1(4) s	0+
¹⁰¹Zr	40	61	100.92114(3)	2.3(1) s	3/2+
¹⁰²Zr	40	62	101.92298(5)	2.9(2) s	0+
¹⁰³Zr	40	63	102.92660(12)	1.3(1) s	(5/2-)
¹⁰⁴Zr	40	64	103.92878(43)#	1.2(3) s	0+
¹⁰⁵Zr	40	65	104.93305(43)#	0.6(1) s
¹⁰⁶Zr	40	66	105.93591(54)#	200# ms [>300 ns]	0+
¹⁰⁷Zr	40	67	106.94075(32)#	150# ms [>300 ns]
¹⁰⁸Zr	40	68	107.94396(64)#	80# ms [>300 ns]	0+
¹⁰⁹Zr	40	69	108.94924(54)#	60# ms [>300 ns]
¹¹⁰Zr	40	70	109.95287(86)#	30# ms [>300 ns]	0+

Notes

Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
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.