Isotopes of antimony

Antimony (₅₁Sb) occurs naturally as two stable isotopes, ¹²¹Sb (57.21%) and ¹²³Sb (42.79%). There are 37 artificial radioactive isotopes known with mass numbers 104 to 142, the lightest two of which (^104-105Sb) are beyond the proton drip line. Isotopes that are lighter than the stable isotopes tend to decay by β⁺, and those that are heavier tend to decay by β⁻; the intermediate ¹²²Sb is observed to decay in both ways.

Isotopes of antimony (₅₁Sb)

Main isotopes			Decay
Isotope	abundance	half-life (t_1/2)	mode	product
¹²¹Sb	57.2%	stable
¹²³Sb	42.8%	stable
¹²⁵Sb	synth	2.758 y	β⁻	¹²⁵Te

Standard atomic weight A_r°(Sb)

121.760±0.001
121.76±0.01 (abridged)

The most stable radioisotope of antimony is the minor fission product ¹²⁵Sb, with a half-life of 2.758 years; ¹²⁴Sb, with half-life 60.20 days; and ¹²⁶Sb, with half-life 12.35 days. All other isotopes have half-lives less than 4 days, most less than an hour. Of the numerous isomers reported, the longest-lived is ^120m1Sb with half-life 5.76 days; this nuclide has not been confirmed not to be the ground state.

List of isotopes

Nuclide	Z	N	Isotopic mass (Da)	Half-life	Decay mode	Daughter isotope	Spin and parity	Natural abundance (mole fraction)
Nuclide	Excitation energy			Half-life	Decay mode	Daughter isotope	Spin and parity	Normal proportion	Range of variation
¹⁰⁴Sb	51	53	103.936331(24)	470(130) ms	β⁺?	¹⁰⁴Sn
					p (<7%)	¹⁰³Sn
					β⁺, p (<7%)	¹⁰³In
					α?	¹⁰⁰In
¹⁰⁵Sb	51	54	104.931277(23)	1.12(16) s	β⁺ (>99.9%)	¹⁰⁵Sn	(5/2+)
					p (<0.1%)	¹⁰⁴Sn
					β⁺, p?	¹⁰⁴In
¹⁰⁶Sb	51	55	105.9286380(80)	0.6(2) s	β⁺	¹⁰⁶Sn	(2+)
^106mSb	103.5(3) keV			226(14) ns	IT	¹⁰⁶Sb	(4+)
¹⁰⁷Sb	51	56	106.9241506(45)	4.0(2) s	β⁺	¹⁰⁷Sn	5/2+#
¹⁰⁸Sb	51	57	107.9222267(59)	7.4(3) s	β⁺	¹⁰⁸Sn	(4+)
¹⁰⁹Sb	51	58	108.9181412(57)	17.2(5) s	β⁺	¹⁰⁹Sn	5/2+#
¹¹⁰Sb	51	59	109.9168543(64)	23.6(3) s	β⁺	¹¹⁰Sn	(3+)
¹¹¹Sb	51	60	110.9132182(95)	75(1) s	β⁺	¹¹¹Sn	(5/2+)
¹¹²Sb	51	61	111.912400(19)	53.5(6) s	β⁺	¹¹²Sn	(3+)
^112mSb	825.9(4) keV			536(22) ns	IT	¹¹²Sb	(8−)
¹¹³Sb	51	62	112.909375(18)	6.67(7) min	β⁺	¹¹³Sn	5/2+
¹¹⁴Sb	51	63	113.909289(21)	3.49(3) min	β⁺	¹¹⁴Sn	3+
^114mSb	495.5(7) keV			219(12) μs	IT	¹¹⁴Sb	(8−)
¹¹⁵Sb	51	64	114.906598(17)	32.1(3) min	β⁺	¹¹⁵Sn	5/2+
^115mSb	2796.26(9) keV			159(3) ns	IT	¹¹⁵Sb	(19/2)−
¹¹⁶Sb	51	65	115.9067927(55)	15.8(8) min	β⁺	¹¹⁶Sn	3+
^116m1Sb	93.99(5) keV			194(4) ns	IT	¹¹⁶Sb	1+
^116m2Sb	390(40) keV			60.3(6) min	β⁺	¹¹⁶Sn	8−
¹¹⁷Sb	51	66	116.9048415(91)	2.97(2) h	β⁺	¹¹⁷Sn	5/2+
^117m1Sb	3130.76(19) keV			355(17) μs	IT	¹¹⁷Sb	(25/2)+
^117m2Sb	3230.7(2) keV			290(5) ns	IT	¹¹⁷Sb	(23/2−)
¹¹⁸Sb	51	67	117.9055322(32)	3.6(1) min	β⁺	¹¹⁸Sn	1+
^118m1Sb	50.814(21) keV			20.6(6) μs	IT	¹¹⁸Sb	3+
^118m2Sb	250(6) keV			5.01(3) h	β⁺	¹¹⁸Sn	8−
¹¹⁹Sb	51	68	118.9039441(75)	38.19(22) h	EC	¹¹⁹Sn	5/2+
^119m1Sb	2553.6(3) keV			130(3) ns	IT	¹¹⁹Sb	19/2−
^119m2Sb	2841.7(4) keV			835(81) ms	IT	¹¹⁹Sb	25/2+
¹²⁰Sb	51	69	119.9050803(77)	15.89(4) min	β⁺	¹²⁰Sn	1+
^120m1Sb	0(100)# keV			5.76(2) d	β⁺	¹²⁰Sn	8−
^120m2Sb	78.16(5) keV			246(2) ns	IT	¹²⁰Sb	(3+)
^120m3Sb	2328(100)# keV			400(8) ns	IT	¹²⁰Sb	13+
¹²¹Sb	51	70	120.9038114(27)	Stable			5/2+	0.5721(5)
^121mSb	2751(17) keV			179(6) μs	IT	¹²¹Sb	(25/2+)
¹²²Sb	51	71	121.9051693(27)	2.7238(2) d	β⁻ (97.59%)	¹²²Te	2−
¹²²Sb	51	71	121.9051693(27)	2.7238(2) d	β⁺ (2.41%)	¹²²Sn	2−
^122m1Sb	61.4131(5) keV			1.86(8) μs	IT	¹²²Sb	3+
^122m2Sb	137.4726(8) keV			0.53(3) ms	IT	¹²²Sb	5+
^122m3Sb	163.5591(17) keV			4.191(3) min	IT	¹²²Sb	8−
¹²³Sb	51	72	122.9042153(15)	Stable			7/2+	0.4279(5)
^123m1Sb	2237.8(3) keV			214(3) ns	IT	¹²³Sb	19/2−
^123m2Sb	2613.4(4) keV			65(1) μs	IT	¹²³Sb	23/2+
¹²⁴Sb	51	73	123.9059371(15)	60.20(3) d	β⁻	¹²⁴Te	3−
^124m1Sb	10.8627(8) keV			93(5) s	IT (75%)	¹²⁴Sb	5+
^124m1Sb	10.8627(8) keV			93(5) s	β⁻ (25%)	¹²⁴Te	5+
^124m2Sb	36.8440(14) keV			20.2(2) min	IT	^124m1Sb	(8)−
^124m3Sb	40.8038(7) keV			3.2(3) μs	IT	¹²⁴Sb	(3+)
¹²⁵Sb	51	74	124.9052543(27)	2.7576(11) y	β⁻	¹²⁵Te	7/2+
^125m1Sb	1971.25(20) keV			4.1(2) μs	IT	¹²⁵Sb	15/2−
^125m2Sb	2112.1(3) keV			28.5(5) μs	IT	¹²⁵Sb	19/2−
^125m3Sb	2471.0(4) keV			277.0(64) ns	IT	¹²⁵Sb	(23/2)+
¹²⁶Sb	51	75	125.907253(34)	12.35(6) d	β⁻	¹²⁶Te	8−
^126m1Sb	17.7(3) keV			19.15(8) min	β⁻ (86%)	¹²⁶Te	5+
^126m1Sb	17.7(3) keV			19.15(8) min	IT (14%)	¹²⁶Sb	5+
^126m2Sb	40.4(3) keV			~11 s	IT	^126m1Sb	3−
^126m3Sb	104.6(3) keV			553(5) ns	IT	¹²⁶Sb	3+
^126m4Sb	1810.7(17) keV			90(16) ns	IT	¹²⁶Sb	(13+)
¹²⁷Sb	51	76	126.9069256(55)	3.85(5) d	β⁻	¹²⁷Te	7/2+
^127m1Sb	1920.19(21) keV			11.7(1) μs	IT	¹²⁷Sb	15/2−
^127m2Sb	2324.7(4) keV			269(5) ns	IT	¹²⁷Sb	23/2+
¹²⁸Sb	51	77	127.909146(20)	9.05(4) h	β⁻	¹²⁸Te	8−
^128m1Sb	10(6) keV			10.41(18) min	β⁻ (96.4%)	¹²⁸Te	5+
^128m1Sb	10(6) keV			10.41(18) min	IT (3.6%)	¹²⁸Sb	5+
^128m2Sb	1617.3(7) keV			500(20) ns	IT	¹²⁸Sb	(11+)
^128m3Sb	1769.9(12) keV			217(7) ns	IT	¹²⁸Sb	(13+)
¹²⁹Sb	51	78	128.909147(23)	4.366(26) h	β⁻	¹²⁹Te	7/2+
^129m1Sb	1851.31(6) keV			17.7(1) min	β⁻ (85%)	¹²⁹Te	19/2−
^129m1Sb	1851.31(6) keV			17.7(1) min	IT (15%)	¹²⁹Sb	19/2−
^129m2Sb	1861.06(5) keV			2.23(17) μs	IT	¹²⁹Sb	15/2−
^129m3Sb	2139.4(3) keV			0.89(3) μs	IT	¹²⁹Sb	23/2+
¹³⁰Sb	51	79	129.911663(15)	39.5(8) min	β⁻	¹³⁰Te	8−
^130m1Sb	4.80(20) keV			6.3(2) min	β⁻	¹³⁰Te	4+
^130m2Sb	84.67(4) keV			800(100) ns	IT	¹³⁰Sb	6−
^130m3Sb	1508(1) keV			600(15) ns	IT	¹³⁰Sb	(11+)
^130m4Sb	1544.7(5) keV			1.25(1) μs	IT	¹³⁰Sb	(13+)
¹³¹Sb	51	80	130.9119893(22)	23.03(4) min	β⁻	¹³¹Te	7/2+
^131m1Sb	1676.06(6) keV			64.2(26) μs	IT	¹³¹Sb	15/2−
^131m2Sb	1687.2(9) keV			4.3(8) μs	IT	¹³¹Sb	19/2−
^131m3Sb	2165.6(15) keV			0.97(3) μs	IT	¹³¹Sb	23/2+
¹³²Sb	51	81	131.9145141(29)	2.79(7) min	β⁻	¹³²Te	(4)+
^132m1Sb	139.3(20) keV			4.10(5) min	β⁻	¹³²Te	(8−)
^132m2Sb	254.5(3) keV			102(4) ns	IT	¹³²Sb	(6−)
¹³³Sb	51	82	132.9152721(34)	2.34(5) min	β⁻	¹³³Te	(7/2+)
^133mSb	4541(9) keV			16.54(19) μs	IT	¹³³Sb	(21/2+)
¹³⁴Sb	51	83	133.9205373(33)	674(4) ms	β⁻	¹³⁴Te	(0-)
¹³⁴Sb	51	83	133.9205373(33)	674(4) ms	β⁻, n?	¹³³Te	(0-)
^134mSb	279(1) keV			10.01(4) s	β⁻ (99.91%)	¹³⁴Te	(7−)
^134mSb	279(1) keV			10.01(4) s	β⁻, n (0.088%)	¹³³Te	(7−)
¹³⁵Sb	51	84	134.9251844(28)	1.668(9) s	β⁻ (80.9%)	¹³⁵Te	(7/2+)
¹³⁵Sb	51	84	134.9251844(28)	1.668(9) s	β⁻, n (19.1%)	¹³⁴Te	(7/2+)
¹³⁶Sb	51	85	135.9307490(63)	0.923(14) s	β⁻ (75.2%)	¹³⁶Te	(1−)
					β⁻, n (24.7%)	¹³⁵Te
					β⁻, 2n (0.14%)	¹³⁴Te
^136mSb	269.3(5) keV			570(5) ns	IT	¹³⁶Sb	(6−)
¹³⁷Sb	51	86	136.935523(56)	497(21) ms	β⁻ (51%)	¹³⁷Te	7/2+#
					β⁻, n (49%)	¹³⁶Te
					β⁻, 2n?	¹³⁵Te
¹³⁸Sb	51	87	137.94133(32)#	333(7) ms	β⁻, n (72%)	¹³⁷Te	(3−)
					β⁻ (28%)	¹³⁸Te
					β⁻, 2n?	¹³⁶Te
¹³⁹Sb	51	88	138.94627(43)#	182(9) ms	β⁻, n (90%)	¹³⁸Te	7/2+#
					β⁻ (10%)	¹³⁹Te
					β⁻, 2n?	¹³⁷Te
¹⁴⁰Sb	51	89	139.95235(64)#	170(6) ms	β⁻ (69%)	¹⁴⁰Te	(3−)
					β⁻, n (23%)	¹³⁹Te
					β⁻, 2n (7.6%)	¹³⁸Te
^140mSb	330(30)# keV			41(8) μs	IT	¹⁴⁰Sb	(6−,7−)
¹⁴¹Sb	51	90	140.95755(54)#	103(29) ms	β⁻	¹⁴¹Te	7/2+#
					β⁻, n?	¹⁴⁰Te
					β⁻, 2n?	¹³⁹Te
¹⁴²Sb	51	91	141.96392(32)#	80(50) ms	β⁻	¹⁴²Te
					β⁻, n?	¹⁴¹Te
					β⁻, 2n?	¹⁴⁰Te
This table header & footer: view

^mSb – Excited nuclear isomer.
( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
# – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
Modes of decay:

EC: Electron capture

IT: Isomeric transition

n: Neutron emission

p: Proton emission
Bold italics symbol as daughter – Daughter product is nearly stable.
Bold symbol as daughter – Daughter product is stable.
( ) spin value – Indicates spin with weak assignment arguments.
# – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
Order of ground state and isomer is uncertain.
Fission product

EC:	Electron capture
IT:	Isomeric transition
n:	Neutron emission
p:	Proton emission

List of isotopes

See also