Прометиумот (61Pm) — вештачки елемент, освен во трагови како производ на спонтано цепење од 238U и 235U и алфа-распад од 151Eu, и затоа не може да се даде стандардна атомска тежина. Како и сите вештачки елементи, тој нема стабилни изотопи. За прв пат е синтетизиран во 1945 година.
Карактеризирани се 41 радиоизотопи, од кои најстабилни се 145Pm со полураспад од 17,7 години, 146Pm со полураспад од 5,53 години и 147Pm со полураспад од 2,6234 години. Сите преостанати радиоактивни изотопи имаат полураспад помал од 365 дена, а поголемиот дел од нив имаат полураспад помал од 30 секунди. Овој елемент има и 18 мета состојби со најстабилни 148mPm (t1/2 41,29 дена), 152m2 Pm (t1/2 13,8 минути) и 152mPm (t1/2 7,52 минути).
Изотопите на прометиум се движат по маса од 126 до 166. Примарниот режим на распаѓање за 146Pm и полесни изотопи е електронски зафат, а примарниот режим за потешки изотопи е бета-распад. Примарните распадни производи пред 146Pm се изотопи на неодимиумот, а примарните производи потоа се изотопи на самариумот.
Список на изотопи
|-id=Promethium-128 | rowspan=2|128Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 67 | rowspan=2|127.94823(32)# | rowspan=2|1.0(3) s | β+ (?%) | 128Nd | rowspan=2|4+# | rowspan=2| |- | β+, п (?%) | 127Pr |-id=Promethium-129 | 129Pm | style="text-align:right" | 61 | style="text-align:right" | 68 | 128.94291(32)# | 2.4(9) s | β+ | 129Nd | 5/2+# | |-id=Promethium-130 | rowspan=2|130Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 69 | rowspan=2|129.94045(22)# | rowspan=2|2.6(2) s | β+ (?%) | 130Nd | rowspan=2|(5+, 6+, 4+) | rowspan=2| |- | β+, p (?%) | 129Pr |-id=Promethium-131 | 131Pm | style="text-align:right" | 61 | style="text-align:right" | 70 | 130.93583(22)# | 6.3(8) s | β+ | 131Nd | (11/2−) | |-id=Promethium-132 | rowspan=2|132Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 71 | rowspan=2|131.93384(16)# | rowspan=2|6.2(6) s | β+ | 132Nd | rowspan=2|(3+) | rowspan=2| |- | β+, p (5×10−5%) | 131Pr |-id=Promethium-133 | 133Pm | style="text-align:right" | 61 | style="text-align:right" | 72 | 132.929782(54) | 13.5(21) s | β+ | 133Nd | (3/2+) | |-id=Promethium-133m | style="text-indent:1em" | 133mPm | colspan="3" style="text-indent:2em" | 129.7(7) keV | 8# s
| (11/2−) | |-id=Promethium-134 | 134Pm | style="text-align:right" | 61 | style="text-align:right" | 73 | 133.928326(45) | 22(1) s | β+ | 134Nd | (5+) | |-id=Promethium-134m1 | style="text-indent:1em" | 134m1Pm | colspan="3" style="text-indent:2em" | 50(50)# keVРедоследот на основната состојба и изомерот е непознат. | ~5 s | β+ | 134Nd | (2+) | |-id=Promethium-134m2 | style="text-indent:1em" | 134m2Pm | colspan="3" style="text-indent:2em" | 120(50)# keV | 20(1) μs | ИП | 134Pm | (7−) | |-id=Promethium-135 | 135Pm | style="text-align:right" | 61 | style="text-align:right" | 74 | 134.924785(89) | 49(3) s | β+ | 135Nd | (3/2+, 5/2+) | |-id=Promethium-135m | style="text-indent:1em" | 135mPm | colspan="3" style="text-indent:2em" | 240(100)# keV | 40(3) s | β+ | 135Nd | (11/2−) | |-id=Promethium-136 | 136Pm | style="text-align:right" | 61 | style="text-align:right" | 75 | 135.923596(74) | 107(6) s | β+ | 136Nd | 7+# | |-id=Promethium-136m1 | style="text-indent:1em" | 136m1Pm | colspan="3" style="text-indent:2em" | 100(120) keV | 90(35) s | β+ | 136Nd | 2+# | |-id=Promethium-136m2 | style="text-indent:1em" | 136m2Pm | colspan="3" style="text-indent:2em" | 42.7(2) keV | 1.5(1) μs | ИП | 136Pm | 7−# | |-id=Promethium-137 | 137Pm | style="text-align:right" | 61 | style="text-align:right" | 76 | 136.920480(14) | 2# min
| 5/2−# | |-id=Promethium-137m | style="text-indent:1em" | 137mPm | colspan="3" style="text-indent:2em" | 160(50) keV | 2.4(1) min | β+ | 137Nd | 11/2− | |-id=Promethium-138 | 138Pm | style="text-align:right" | 61 | style="text-align:right" | 77 | 137.919576(12) | 3.24(5) min | β+ | 138Nd | 3−# | |-id=Promethium-139 | 139Pm | style="text-align:right" | 61 | style="text-align:right" | 78 | 138.916799(15) | 4.15(5) min | β+ | 139Nd | (5/2)+ | |-id=Promethium-139m | style="text-indent:1em" | 139mPm | colspan="3" style="text-indent:2em" | 188.7(3) keV | 180(20) ms | ИП | 139Pm | (11/2)− | |-id=Promethium-140 | 140Pm | style="text-align:right" | 61 | style="text-align:right" | 79 | 139.916036(26) | 9.2(2) s | β+ | 140Nd | 1+ | |-id=Promethium-140m | style="text-indent:1em" | 140mPm | colspan="3" style="text-indent:2em" | 429(28) keV | 5.95(5) min | β+ | 140Nd | 8− | |-id=Promethium-141 | 141Pm | style="text-align:right" | 61 | style="text-align:right" | 80 | 140.913555(15) | 20.90(5) min | β+ | 141Nd | 5/2+ | |-id=Promethium-141m1 | style="text-indent:1em" | 141m1Pm | colspan="3" style="text-indent:2em" | 628.62(7) keV | 630(20) ns | ИП | 141Pm | 11/2− | |-id=Promethium-141m2 | style="text-indent:1em" | 141m2Pm | colspan="3" style="text-indent:2em" | 2530.75(17) keV | >2 μs | ИП | 141Pm | (23/2+) | |-id=Promethium-142 | rowspan=2|142Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 81 | rowspan=2|141.912891(25) | rowspan=2|40.5(5) s | β+ (77.1%) | rowspan=2|142Nd | rowspan=2|1+ | rowspan=2| |- | ЕЗ (22.9%) |-id=Promethium-142m1 | style="text-indent:1em" | 142m1Pm | colspan="3" style="text-indent:2em" | 883.17(16) keV | 2.0(2) ms | ИП | 142Pm | (8)− | |-id=Promethium-142m2 | style="text-indent:1em" | 142m2Pm | colspan="3" style="text-indent:2em" | 2828.7(6) keV | 67(5) μs | ИП | 142Pm | (13−) | |-id=Promethium-143 | rowspan=2|143Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 82 | rowspan=2 | 142.9109381(32) | rowspan=2 | 265(7) d | ЕЗ | rowspan=2 | 143Nd | rowspan=2 | 5/2+ | rowspan=2 | |- | β+ (<5.7×10−6%) |-id=Promethium-144 | rowspan=2|144Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 83 | rowspan=2 | 143.9125962(31) | rowspan=2 | 363(14) d | EC | rowspan=2 | 144Nd | rowspan=2 | 5− | rowspan=2 | |- | β+ (<8×10−5%) |-id=Promethium-144m1 | style="text-indent:1em" | 144m1Pm | colspan="3" style="text-indent:2em" | 840.90(5) keV | 780(200) ns | ИП | 144Pm | (9)+ | |-id=Promethium-144m2 | style="text-indent:1em" | 144m2Pm | colspan="3" style="text-indent:2em" | 8595.8(22) keV | ~2.7 μs | ИП | 144Pm | (27+) | |-id=Promethium-145 | rowspan=2|145Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 84 | rowspan=2|144.9127557(30) | rowspan=2|17.7(4) y | EC | 145Nd | rowspan=2|5/2+ | rowspan=2| |- | α (2.8×10−7%) | 141Pr |-id=Promethium-146 | rowspan=2|146Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 85 | rowspan=2|145.9147022(46) | rowspan=2|5.53(5) y | ЕЗ (66.0%) | 146Nd | rowspan=2|3− | rowspan=2| |- | β− (34.0%) | 146Sm |- | 147PmПроизводи на цепење | style="text-align:right" | 61 | style="text-align:right" | 86 | 146.9151449(14) | 2.6234(2) y | β− | 147Sm | 7/2+ | Трагиспонтан производ на 232Th, 235U, 238U и алфа ќерка на првобитниот 151Eu |-id=Promethium-148 | 148Pm | style="text-align:right" | 61 | style="text-align:right" | 87 | 147.9174811(61) | 5.368(7) d | β− | 148Sm | 1− | |-id=Promethium-148m | rowspan=2 style="text-indent:1em" | 148mPm | rowspan=2 colspan="3" style="text-indent:2em" | 137.9(3) keV | rowspan=2|41.29(11) d | β− (95.8%) | 148Sm | rowspan=2|5−, 6− | rowspan=2| |- | ИП (4.2%) | 148Pm |-id=Promethium-149 | 149Pm | style="text-align:right" | 61 | style="text-align:right" | 88 | 148.9183415(23) | 53.08(5) h | β− | 149Sm | 7/2+ | |-id=Promethium-149m | style="text-indent:1em" | 149mPm | colspan="3" style="text-indent:2em" | 240.214(7) keV | 35(3) μs | ИП | 149Pm | 11/2− | |-id=Promethium-150 | 150Pm | style="text-align:right" | 61 | style="text-align:right" | 89 | 149.920990(22) | 2.698(15) h | β− | 150Sm | (1−) | |-id=Promethium-151 | 151Pm | style="text-align:right" | 61 | style="text-align:right" | 90 | 150.9212166(49) | 28.40(4) h | β− | 151Sm | 5/2+ | |-id=Promethium-152 | 152Pm | style="text-align:right" | 61 | style="text-align:right" | 91 | 151.923505(28) | 4.12(8) min | β− | 152Sm | 1+ | |-id=Promethium-152m | style="text-indent:1em" | 152mPm | colspan="3" style="text-indent:2em" | 140(90) keV | 7.52(8) min | β− | 152Sm | 4(−) | |-id=Promethium-153 | 153Pm | style="text-align:right" | 61 | style="text-align:right" | 92 | 152.9241563(97) | 5.25(2) min | β− | 153Sm | 5/2− | |-id=Promethium-154 | 154Pm | style="text-align:right" | 61 | style="text-align:right" | 93 | 153.926713(27) | 2.68(7) min | β− | 154Sm | (4+) | |-id=Promethium-154m | style="text-indent:1em" | 154mPm | colspan="3" style="text-indent:2em" | −230(50) keV | 1.73(10) min | β− | 154Sm | (1−) | |-id=Promethium-155 | 155Pm | style="text-align:right" | 61 | style="text-align:right" | 94 | 154.9281370(51) | 41.5(2) s | β− | 155Sm | (5/2−) | |-id=Promethium-156 | 156Pm | style="text-align:right" | 61 | style="text-align:right" | 95 | 155.9311141(13) | 27.4(5) s | β− | 156Sm | 4+ | |-id=Promethium-156m | rowspan=2 style="text-indent:1em" | 156mPm | rowspan=2 colspan="3" style="text-indent:2em" | 150.30(10) keV | rowspan=2|2.3(20) s | ИП (98%) | 156Pm | rowspan=2|1+# | rowspan=2| |- | β− (2%) | 156Sm |-id=Promethium-157 | 157Pm | style="text-align:right" | 61 | style="text-align:right" | 96 | 156.9331213(75) | 10.56(10) s | β− | 157Sm | (5/2−) | |-id=Promethium-158 | 158Pm | style="text-align:right" | 61 | style="text-align:right" | 97 | 157.93654695(95) | 4.8(5) s | β− | 158Sm | (0+,1+)# | |-id=Promethium-158m | style="text-indent:1em" | 158mPm | colspan="3" style="text-indent:2em" | 150(50)# keV | >16 μs | ИП | 158Pm | 5+# | |-id=Promethium-159 | 159Pm | style="text-align:right" | 61 | style="text-align:right" | 98 | 158.939286(11) | | β− | 159Sm | (5/2−) | |-id=Promethium-159m | rowspan=2 style="text-indent:1em" | 159mPm | rowspan=2 colspan="3" style="text-indent:2em" | 1465.0(5) keV | rowspan=2|4.42(17) μs | ИП | 159Pm | rowspan=2|17/2+# | rowspan=2| |- | β−, n (<0.6%) | 158Sm |-id=Promethium-160 | rowspan=2|160Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 99 | rowspan=2|159.9432153(22) | rowspan=2| | β− | 160Sm | rowspan=2|6−# | rowspan=2| |- | β−, n (<0.1%) | 159Sm |-id=Promethium-160m | style="text-indent:1em" | 160mPm | colspan="3" style="text-indent:2em" | 191(11) keV | >700 ms
| 1−# | |-id=Promethium-161 | rowspan=2|161Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 100 | rowspan=2|160.9462298(97) | rowspan=2| | β− (98.91%) | 161Sm | rowspan=2|(5/2−) | rowspan=2| |- | β−, n (1.09%) | 160Sm |-id=Promethium-161m | style="text-indent:1em" | 161mPm | colspan="3" style="text-indent:2em" | 965.9(9) keV | 890(90) ns | ИП | 161Pm | (13/2+) | |-id=Promethium-162 | rowspan=2|162Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 101 | rowspan=2|161.95057(32)# | rowspan=2| | β− (98.21%) | 162Sm | rowspan=2| 2+# | rowspan=2| |- | β−, n (1.79%) | 161Sm |-id=Promethium-163 | rowspan=2|163Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 102 | rowspan=2|162.95388(43)# | rowspan=2| | β− (95%) | 163Sm | rowspan=2|5/2−# | rowspan=2| |- | β−, n (5.00%) | 162Sm |-id=Promethium-164 | rowspan=2|164Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 103 | rowspan=2|163.95882(43)# | rowspan=2| | β− (93.82%) | 164Sm | rowspan=2|5−# | rowspan=2| |- | β−, n (6.18%) | 163Sm |-id=Promethium-165 | rowspan=2|165Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 104 | rowspan=2|164.96278(54)# | rowspan=2| | β− (86.74%) | 165Sm | rowspan=2|5/2−# | rowspan=2| |- | β−, n (13.26%) | 164Sm |-id=Promethium-166 | rowspan=2|166Pm | rowspan=2 style="text-align:right" | 61 | rowspan=2 style="text-align:right" | 105 | rowspan=2| | rowspan=2| | β− | 166Sm | rowspan=2| | rowspan=2| |- | β−, n (<52%) | 165Sm
Стабилност на изотопи на прометиум