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[1] Decay Isotope abun­dance half-life (t1/2) mode pro­duct 121Sb 57.2% stable 123Sb 42.8% stable 125Sb synth 2.758 y β− 125Te
Standard atomic weight Ar°(Sb)
	121.760±0.001[2] 121.76±0.01 (abridged)[3]
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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 [n 1]	Z	N	Isotopic mass (Da)[4] [n 2][n 3]	Half-life[1]	Decay mode[1] [n 4]	Daughter isotope [n 5][n 6]	Spin and parity[1] [n 7][n 8]	Natural abundance (mole fraction)
	Excitation energy[n 8]							Normal proportion[1]	Range of variation
104Sb	51	53	103.93634(11)#	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[n 9]	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[n 10]	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−
					β+ (2.41%)	122Sn
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[n 10]	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+
					β− (25%)	124Te
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[n 10]	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+
					IT (14%)	126Sb
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[n 10]	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+
					IT (3.6%)	128Sb
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−
					IT (15%)	129Sb
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)[5]	2.79(7) min	β−	132Te	(4)+
132m1Sb	139.3(20) keV[5]			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-)
					β−, n?	133Te
134mSb	279(1) keV			10.01(4) s	β− (99.91%)	134Te	(7−)
					β−, n (0.088%)	133Te
135Sb	51	84	134.9251844(28)	1.668(9) s	β− (80.9%)	135Te	(7/2+)
					β−, n (19.1%)	134Te
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

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

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

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

See also

Daughter products other than antimony

• Isotopes of tellurium
• Isotopes of tin
• Isotopes of indium