Isotopes of technetium

Technetium (₄₃Tc) is one of the two elements with Z < 83 that have no stable isotopes; the other such element is promethium.^[2] It is primarily artificial, with only trace quantities existing in nature produced by spontaneous fission (there are an estimated 2.5×10⁻¹³ grams of ⁹⁹Tc per gram of pitchblende)^[3] or neutron capture by molybdenum. The first isotopes to be synthesized were ⁹⁷Tc and ⁹⁹Tc^{[disputed – discuss]} in 1936, the first artificial element to be produced. The most stable radioisotopes are ⁹⁷Tc (half-life of 4.21 million years), ⁹⁸Tc (half-life: 4.2 million years), and ⁹⁹Tc (half-life: 211,100 years).^[4][5]

Isotopes of technetium (₄₃Tc)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 95mTc synth 61.96 d β+ 95Mo IT 95Tc 96Tc synth 4.28 d β+ 96Mo 97Tc synth 4.21×106 y ε 97Mo 97mTc synth 91.1 d IT 97Tc ε 97Mo 98Tc synth 4.2×106 y β− 98Ru 99Tc trace 2.111×105 y β− 99Ru 99mTc synth 6.01 h IT 99Tc β− 99Ru

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Thirty-three other radioisotopes have been characterized with atomic masses ranging from ⁸⁵Tc to ¹²⁰Tc.^[6] Most of these have half-lives that are less than an hour; the exceptions are ⁹³Tc (half-life: 2.75 hours), ⁹⁴Tc (half-life: 4.883 hours), ⁹⁵Tc (half-life: 20 hours), and ⁹⁶Tc (half-life: 4.28 days).^[7]

Technetium also has numerous meta states. ^97mTc is the most stable, with a half-life of 91.0 days (0.097 MeV).^[4] This is followed by ^95mTc (half-life: 61 days, 0.038 MeV) and ^99mTc (half-life: 6.04 hours, 0.143 MeV). ^99mTc only emits gamma rays, subsequently decaying to ⁹⁹Tc.^[7]

For isotopes lighter than ⁹⁸Tc, the primary decay mode is electron capture to isotopes of molybdenum. For the heavier isotopes, the primary mode is beta emission to isotopes of ruthenium, with the exception that ¹⁰⁰Tc can decay both by beta emission and electron capture.^[7][8]

Technetium-99m is the hallmark technetium isotope employed in the nuclear medicine industry. Its low-energy isomeric transition, which yields a gamma-ray at ~140.5 keV, is ideal for imaging using Single Photon Emission Computed Tomography (SPECT). Several technetium isotopes, such as ^94mTc, ⁹⁵Tc, and ⁹⁶Tc, which are produced via (p,n) reactions using a cyclotron on molybdenum targets, have also been identified as potential Positron Emission Tomography (PET) or gamma-emitting agents for medical imaging.^[9][10][11] Technetium-101 has been produced using a D-D fusion-based neutron generator from the ¹⁰⁰Mo(n,γ)¹⁰¹Mo reaction on natural molybdenum and subsequent beta-minus decay of ¹⁰¹Mo to ¹⁰¹Tc. Despite its shorter half-life (i.e., 14.22 min), ¹⁰¹Tc exhibits unique decay characteristics suitable for radioisotope diagnostic or therapeutic procedures, where it has been proposed that its implementation, as a supplement for dual-isotopic imaging or replacement for ^99mTc, could be performed by on-site production and dispensing at the point of patient care.^[12]

Technetium-99 is the most common and most readily available isotope, as it is a major fission product from fission of actinides like uranium and plutonium with a fission product yield of 6% or more, and in fact the most significant long-lived fission product. Lighter isotopes of technetium are almost never produced in fission because the initial fission products normally have a higher neutron/proton ratio than is stable for their mass range, and therefore undergo beta decay until reaching the ultimate product. Beta decay of fission products of mass 95–98 stops at the stable isotopes of molybdenum of those masses and does not reach technetium. For mass 100 and greater, the technetium isotopes of those masses are very short-lived and quickly beta decay to isotopes of ruthenium. Therefore, the technetium in spent nuclear fuel is practically all ⁹⁹Tc. In the presence of fast neutrons a small amount of ⁹⁸
Tc will be produced by (n,2n) "knockout" reactions. If nuclear transmutation of fission-derived Technetium or Technetium waste from medical applications is desired, fast neutrons are therefore not desirable as the long lived ⁹⁸
Tc increases rather than reducing the longevity of the radioactivity in the material.

One gram of ⁹⁹Tc produces 6.2×10⁸ disintegrations a second (that is, 0.62 GBq/g).^[13]

Technetium has no primordial isotopes and does not occur in nature in significant quantities, and thus a standard atomic weight cannot be given.

List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da)[14] [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]	Isotopic abundance
	Excitation energy[n 8]
86Tc	43	43	85.94464(32)#	55(7) ms	β+	86Mo	(0+)
86mTc	1524(10) keV			1.10(12) μs	IT	86Tc	(6+)
87Tc	43	44	86.9380672(45)	2.14(17) s	β+	87Mo	9/2+#
					β+, p (<0.7%)	86Nb
87mTc	71(1) keV			647(24) ns	IT	87Tc	7/2+#
88Tc	43	45	87.9337942(44)	6.4(8) s	β+	88Mo	(2+)
88m1Tc	70(3) keV			5.8(2) s	β+	88Mo	(6+)
88m2Tc	95(1) keV			146(12) ns	IT	88Tc	(4+)
89Tc	43	46	88.9276486(41)	12.8(9) s	β+	89Mo	(9/2+)
89mTc	62.6(5) keV			12.9(8) s	β+	89Mo	(1/2−)
90Tc	43	47	89.9240739(11)	49.2(4) s	β+	90Mo	(8+)
90mTc	144.0(17) keV			8.7(2) s	β+	90Mo	1+
91Tc	43	48	90.9184250(25)	3.14(2) min	β+	91Mo	(9/2)+
91mTc	139.3(3) keV			3.3(1) min	β+ (99%)	91Mo	(1/2)−
92Tc	43	49	91.9152698(33)	4.25(15) min	β+	92Mo	(8)+
92m1Tc	270.09(8) keV			1.03(6) μs	IT	92Tc	(4+)
92m2Tc	529.42(13) keV			<0.1 μs	IT	92Tc	(3+)
92m3Tc	711.33(15) keV			<0.1 μs	IT	92Tc	1+
93Tc	43	50	92.9102451(11)	2.75(5) h	β+	93Mo	9/2+
93m1Tc	391.84(8) keV			43.5(10) min	IT (77.4%)	93Tc	1/2−
					β+ (22.6%)	93Mo
93m2Tc	2185.16(15) keV			10.2(3) μs	IT	93Tc	(17/2)−
94Tc	43	51	93.9096523(44)	293(1) min	β+	94Mo	7+
94mTc	76(3) keV			52(1) min	β+ (>99.82%)	94Mo	(2)+
					IT (<0.18%)	94Tc
95Tc	43	52	94.9076523(55)	19.258(26) h	β+	95Mo	9/2+
95mTc	38.91(4) keV			61.96(24) d	β+ (96.1%)	95Mo	1/2−
					IT (3.9%)	95Tc
96Tc	43	53	95.9078667(55)	4.28(7) d	β+	96Mo	7+
96mTc	34.23(4) keV			51.5(10) min	IT (98.0%)	96Tc	4+
					β+ (2.0%)	96Mo
97Tc	43	54	96.9063607(44)	4.21(16)×106 y	EC	97Mo	9/2+
97mTc	96.57(6) keV			91.1(6) d	IT (96.06%)	97Tc	1/2−
					EC (3.94%)	97Mo
98Tc	43	55	97.9072112(36)	4.2(3)×106 y	β−	98Ru	6+
98mTc	90.77(16) keV			14.7(5) μs	IT	98Tc	(2,3)−
99Tc[n 9]	43	56	98.90624968(97)	2.111(12)×105 y	β−	99Ru	9/2+	trace
99mTc[n 10]	142.6836(11) keV			6.0066(2) h	IT	99Tc	1/2−
					β− (0.0037%)	99Ru
100Tc	43	57	99.9076527(15)	15.46(19) s	β−	100Ru	1+
					EC (0.0018%)	100Mo
100m1Tc	200.67(4) keV			8.32(14) μs	IT	100Tc	(4)+
100m2Tc	243.95(4) keV			3.2(2) μs	IT	100Tc	(6)+
101Tc	43	58	100.907305(26)	14.22(1) min	β−	101Ru	9/2+
101mTc	207.526(20) keV			636(8) μs	IT	101Tc	1/2−
102Tc	43	59	101.9092072(98)	5.28(15) s	β−	102Ru	1+
102mTc[n 11]	50(50)# keV			4.35(7) min	β−	102Ru	(4+)
103Tc	43	60	102.909174(11)	54.2(8) s	β−	103Ru	5/2+
104Tc	43	61	103.911434(27)	18.3(3) min	β−	104Ru	(3−)
104m1Tc	69.7(2) keV			3.5(3) μs	IT	104Tc	(5−)
104m2Tc	106.1(3) keV			400(20) ns	IT	104Tc	4#
105Tc	43	62	104.911662(38)	7.64(6) min	β−	105Ru	(3/2−)
106Tc	43	63	105.914357(13)	35.6(6) s	β−	106Ru	(1,2)(+#)
107Tc	43	64	106.9154584(93)	21.2(2) s	β−	107Ru	(3/2−)
107m1Tc	30.1(1) keV			3.85(5) μs	IT	107Tc	(1/2+)
107m2Tc	65.72(14) keV			184(3) ns	IT	107Tc	(5/2+)
108Tc	43	65	107.9184935(94)	5.17(7) s	β−	108Ru	(2)+
109Tc	43	66	108.920254(10)	905(21) ms	β− (99.92%)	109Ru	(5/2+)
					β−, n (0.08%)	108Ru
110Tc	43	67	109.923741(10)	900(13) ms	β− (99.96%)	110Ru	(2+,3+)
					β−, n (0.04%)	109Ru
111Tc	43	68	110.925899(11)	350(11) ms	β− (99.15%)	111Ru	5/2+#
					β−, n (0.85%)	110Ru
112Tc	43	69	111.9299417(59)	323(6) ms	β− (98.5%)	112Ru	(2+)
					β−, n (1.5%)	111Ru
112mTc	352.3(7) keV			150(17) ns	IT	112Tc
113Tc	43	70	112.9325690(36)	152(8) ms	β− (97.9%)	113Ru	5/2+#
					β−, n (2.1%)	112Ru
113mTc	114.4(5) keV			527(16) ns	IT	113Tc	5/2−#
114Tc	43	71	113.93709(47)	121(9) ms	β− (98.7%)	114Ru	5+#
					β−, n (1.3%)	113Ru
114mTc[n 11]	160(430) keV			90(20) ms	β− (98.7%)	114Ru	1+#
					β−, n (1.3%)	113Ru
115Tc	43	72	114.94010(21)#	78(2) ms	β−	115Ru	5/2+#
116Tc	43	73	115.94502(32)#	57(3) ms	β−	116Ru	2+#
117Tc	43	74	116.94832(43)#	44.5(30) ms	β−	117Ru	5/2+#
118Tc	43	75	117.95353(43)#	30(4) ms	β−	118Ru	2+#
119Tc	43	76	118.95688(54)#	22(3) ms	β−	119Ru	5/2+#
120Tc	43	77	119.96243(54)#	21(5) ms	β−	120Ru	3+#
121Tc	43	78	120.96614(54)#	22(6) ms	β−	121Ru	5/2+#
122Tc	43	79	121.97176(32)#	13# ms [>550 ns]			1+#
This table header & footer: view

1. ^mTc – 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. Long-lived fission product
10. Used in medicine
11. Order of ground state and isomer is uncertain.

Stability of technetium isotopes

See also: Beta-decay stable isobars

Technetium and promethium are unusual light elements in that they have no stable isotopes. Using the liquid drop model for atomic nuclei, one can derive a semiempirical formula for the binding energy of a nucleus. This formula predicts a "valley of beta stability" along which nuclides do not undergo beta decay. Nuclides that lie "up the walls" of the valley tend to decay by beta decay towards the center (by emitting an electron, emitting a positron, or capturing an electron). For a fixed number of nucleons A, the binding energies lie on one or more parabolas, with the most stable nuclide at the bottom. One can have more than one parabola because isotopes with an even number of protons and an even number of neutrons are more stable than isotopes with an odd number of neutrons and an odd number of protons. A single beta decay then transforms one into the other. When there is only one parabola, there can be only one stable isotope lying on that parabola. When there are two parabolas, that is, when the number of nucleons is even, it can happen (rarely) that there is a stable nucleus with an odd number of neutrons and an odd number of protons (although this happens only in five instances: ²H, ⁶Li, ¹⁰B, ¹⁴N and ^180mTa). However, if this happens, there can be no stable isotope with an even number of neutrons and an even number of protons.

For technetium (Z = 43), the valley of beta stability is centered at around 98 nucleons. However, for every number of nucleons from 94 to 102, there is already at least one stable nuclide of either molybdenum (Z = 42) or ruthenium (Z = 44), and the Mattauch isobar rule states that two adjacent isobars cannot both be stable.^[15] For the isotopes with odd numbers of nucleons, this immediately rules out a stable isotope of technetium, since there can be only one stable nuclide with a fixed odd number of nucleons. For the isotopes with an even number of nucleons, since technetium has an odd number of protons, any isotope must also have an odd number of neutrons. In such a case, the presence of a stable nuclide having the same number of nucleons and an even number of protons rules out the possibility of a stable nucleus.^[15][16]