Rubidium (37Rb) has 35 known isotopes, from 72Rb to 106Rb, with naturally occurring rubidium composed of two: stable 85Rb (72.2%) and radioactive 87Rb (27.8%). The primordial radionuclide 87Rb has a half-life of , beta decaying to stable 87Sr. It is, as the element is, widespread on Earth as rubidium readily substitutes for potassium in all minerals. The decay of 87Rb has been used extensively in dating rocks; see rubidium–strontium dating for a more detailed discussion.
Other than 87Rb, the longest-lived radioisotopes are 83Rb with a half-life of 86.2 days, 84Rb with a half-life of 32.82 days, and 86Rb with a half-life of 18.645 days. All other radioisotopes have half-lives less than a day, most less than 20 minutes. Of the isomeric states the most stable is 82mRb at 6.472 hours.
The ground state of 82Rb has a much shorter half-life of 1.2575 minutes. It is used medically in some cardiac positron emission tomography scans to assess myocardial perfusion. It is synthesized through the longer-lived 82Sr, made in a cyclotron, though a generator. It may be administered as the chloride.
List of isotopes
|-id=Rubidium-72 | 72Rb | style="text-align:right" | 37 | style="text-align:right" | 35 | 71.95885(54)# | style="text-align:center" | 2017 | 103(22) ns | p | 71Kr | 1+#
|-id=Rubidium-73 | 73Rb | style="text-align:right" | 37 | style="text-align:right" | 36 | 72.950605(44) | style="text-align:center" | 1993 | <81 ns | p | 72Kr | 3/2−#
|-id=Rubidium-74 | 74Rb | style="text-align:right" | 37 | style="text-align:right" | 37 | 73.9442659(32) | style="text-align:center" | 1977 | 64.78(3) ms | β+ | 74Kr | 0+
|-id=Rubidium-75 | 75Rb | style="text-align:right" | 37 | style="text-align:right" | 38 | 74.9385732(13) | style="text-align:center" | 1975 | 19.0(12) s | β+ | 75Kr | 3/2−
|-id=Rubidium-76 | rowspan=2|76Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 39 | rowspan=2|75.9350730(10) | rowspan=2 style="text-align:center" | 1969 | rowspan=2|36.5(6) s | β+ | 76Kr | rowspan=2|1− | rowspan=2| | rowspan=2| |- | β+, α (3.8×10−7%) | 72Se |-id=Rubidium-76m | style="text-indent:1em" | 76mRb | colspan="3" style="text-indent:2em" | 316.93(8) keV | style="text-align:center" | 1986 | 3.050(7) μs | IT | 76Rb | (4+)
|-id=Rubidium-77 | 77Rb | style="text-align:right" | 37 | style="text-align:right" | 40 | 76.9304016(14) | style="text-align:center" | 1972 | 3.78(4) min | β+ | 77Kr | 3/2−
|-id=Rubidium-78 | 78Rb | style="text-align:right" | 37 | style="text-align:right" | 41 | 77.9281419(35) | style="text-align:center" | 1968 | 17.66(3) min | β+ | 78Kr | 0+
|-id=Rubidium-78m1 | style="text-indent:1em" | 78m1Rb | colspan="3" style="text-indent:2em" | 46.84(14) keV | style="text-align:center" | 1972 | 910(40) ns | IT | 78Rb | (1−)
|-id=Rubidium-78m2 | rowspan=2 style="text-indent:1em" | 78m2Rb | rowspan=2 colspan="3" style="text-indent:2em" | 111.19(22) keV | rowspan=2 style="text-align:center" | 1996 | rowspan=2|5.74(3) min | β+ (91%) | 78Kr | rowspan=2|4− | rowspan=2| | rowspan=2| |- | IT (9%) | 78Rb |-id=Rubidium-79 | 79Rb | style="text-align:right" | 37 | style="text-align:right" | 42 | 78.9239901(21) | style="text-align:center" | 1957 | 22.9(5) min | β+ | 79Kr | 5/2+
|-id=Rubidium-80 | 80Rb | style="text-align:right" | 37 | style="text-align:right" | 43 | 79.9225164(20) | style="text-align:center" | 1961 | 33.4(7) s | β+ | 80Kr | 1+
|-id=Rubidium-80m | style="text-indent:1em" | 80mRb | colspan="3" style="text-indent:2em" | 493.9(5) keV | style="text-align:center" | 1996 | 1.63(4) μs | IT | 80Rb | (6+)
|-id=Rubidium-81 | 81Rb | style="text-align:right" | 37 | style="text-align:right" | 44 | 80.9189939(53) | style="text-align:center" | 1949 | 4.572(4) h | β+ | 81Kr | 3/2−
|-id=Rubidium-81m | rowspan=2 style="text-indent:1em" | 81mRb | rowspan=2 colspan="3" style="text-indent:2em" | 86.31(7) keV | rowspan=2 style="text-align:center" | 1977 | rowspan=2|30.5(3) min | IT (97.6%) | 81Rb | rowspan=2|9/2+ | rowspan=2| | rowspan=2| |- | β+ (2.4%) | 81Kr |-id=Rubidium-82 | 82Rb | style="text-align:right" | 37 | style="text-align:right" | 45 | 81.9182090(32) | style="text-align:center" | 1949 | 1.2575(2) min | β+ | 82Kr | 1+
|-id=Rubidium-82m | style="text-indent:1em" | 82mRb | colspan="3" style="text-indent:2em" | 69.0(15) keV | style="text-align:center" | 1953 | 6.472(6) h | β+ | 82Kr | 5−
|-id=Rubidium-83 | 83Rb | style="text-align:right" | 37 | style="text-align:right" | 46 | 82.9151142(25) | style="text-align:center" | 1950 | 86.2(1) d | EC | 83Kr | 5/2−
|-id=Rubidium-83m | style="text-indent:1em" | 83mRb | colspan="3" style="text-indent:2em" | 42.0780(20) keV | style="text-align:center" | 1968 | 7.8(7) ms | IT | 83Rb | 9/2+
|-id=Rubidium-84 | rowspan=2|84Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 47 | rowspan=2|83.9143752(24) | rowspan=2 style="text-align:center" | 1947 | rowspan=2|32.82(7) d | β+ (96.1%) | 84Kr | rowspan=2|2− | rowspan=2| | rowspan=2| |- | β− (3.9%) | 84Sr |-id=Rubidium-84m | style="text-indent:1em" | 84mRb | colspan="3" style="text-indent:2em" | 463.59(8) keV | style="text-align:center" | 1950 | 20.26(4) min | IT | 84Rb | 6−
|-id=Rubidium-85 | 85RbFission product | style="text-align:right" | 37 | style="text-align:right" | 48 | 84.9117897360(54) | style="text-align:center" | 1921 | colspan=3 align=center|Stable | 5/2− | 0.7217(2) | |-id=Rubidium-85m | style="text-indent:1em" | 85mRb | colspan="3" style="text-indent:2em" | 514.0065(22) keV | style="text-align:center" | 1952 | 1.015(1) μs | IT | 85Rb | 9/2+
|-id=Rubidium-86 | rowspan=2|86Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 49 | rowspan=2|85.91116744(21) | rowspan=2 style="text-align:center" | 1941 | rowspan=2|18.645(8) d | β− (99.9948%) | 86Sr | rowspan=2|2− | rowspan=2| | rowspan=2| |- | EC (0.0052%) | 86Kr |-id=Rubidium-86m | style="text-indent:1em" | 86mRb | colspan="3" style="text-indent:2em" | 556.05(18) keV | style="text-align:center" | 1951 | 1.017(3) min | IT | 86Rb | 6−
|-id=Rubidium-87 | 87RbPrimordial radionuclideUsed in rubidium–strontium dating | style="text-align:right" | 37 | style="text-align:right" | 50 | 86.909180529(6) | style="text-align:center" | 1921 | 4.97(3)×1010 y | β− | 87Sr | 3/2− | 0.2783(2) | |-id=Rubidium-88 | 88Rb | style="text-align:right" | 37 | style="text-align:right" | 51 | 87.91131559(17) | style="text-align:center" | 1939 | 17.78(3) min | β− | 88Sr | 2−
|-id=Rubidium-88m | style="text-indent:1em" | 88mRb | colspan="3" style="text-indent:2em" | 1373.8(3) keV | style="text-align:center" | 2009 | 123(13) ns | IT | 88Rb | (7+)
|-id=Rubidium-89 | 89Rb | style="text-align:right" | 37 | style="text-align:right" | 52 | 88.9122781(58) | style="text-align:center" | 1940 | 15.32(10) min | β− | 89Sr | 3/2−
|-id=Rubidium-90 | 90Rb | style="text-align:right" | 37 | style="text-align:right" | 53 | 89.9147976(69) | style="text-align:center" | 1951 | 158(5) s | β− | 90Sr | 0−
|-id=Rubidium-90m | rowspan=2 style="text-indent:1em" | 90mRb | rowspan=2 colspan="3" style="text-indent:2em" | 106.90(3) keV | rowspan=2 style="text-align:center" | 1967 | rowspan=2|258(4) s | β− (97.4%) | 90Sr | rowspan=2|3− | rowspan=2| | rowspan=2| |- | IT (2.6%) | 90 Rb |-id=Rubidium-91 | 91Rb | style="text-align:right" | 37 | style="text-align:right" | 54 | 90.9165373(84) | style="text-align:center" | 1951 | 58.2(3) s | β− | 91Sr | 3/2−
|-id=Rubidium-92 | rowspan=2|92Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 55 | rowspan=2|91.9197285(66) | rowspan=2 style="text-align:center" | 1960 | rowspan=2|4.48(3) s | β− (99.99%) | 92Sr | rowspan=2|0− | rowspan=2| | rowspan=2| |- | β−, n (0.0107%) | 91Sr |-id=Rubidium-93 | rowspan=2|93Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 56 | rowspan=2|92.9220393(84) | rowspan=2 style="text-align:center" | 1960 | rowspan=2|5.84(2) s | β− (98.61%) | 93Sr | rowspan=2|5/2− | rowspan=2| | rowspan=2| |- | β−, n (1.39%) | 92Sr |-id=Rubidium-93m | style="text-indent:1em" | 93mRb | colspan="3" style="text-indent:2em" | 4423.1(15) keV | style="text-align:center" | 2010 | 111(11) ns | IT | 93Rb | (27/2−)
|-id=Rubidium-94 | rowspan=2|94Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 57 | rowspan=2|93.9263948(22) | rowspan=2 style="text-align:center" | 1961 | rowspan=2|2.702(5) s | β− (89.7%) | 94Sr | rowspan=2|3− | rowspan=2| | rowspan=2| |- | β−, n (10.3%) | 93Sr |-id=Rubidium-94m1 | style="text-indent:1em" | 94m1Rb | colspan="3" style="text-indent:2em" | 104.2(2) keV | style="text-align:center" | 2008 | 130(15) ns | IT | 94Rb | (0−)
|-id=Rubidium-94m2 | style="text-indent:1em" | 94m2Rb | colspan="3" style="text-indent:2em" | 2074.9(14) keV | style="text-align:center" | 2016 | 107(16) ns | IT | 94Rb | (10−)
|-id=Rubidium-95 | rowspan=2|95Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 58 | rowspan=2|94.929264(22) | rowspan=2 style="text-align:center" | 1967 | rowspan=2|377.7(8) ms | β− (91.3%) | 95Sr | rowspan=2|5/2− | rowspan=2| | rowspan=2| |- | β−, n (8.7%) | 94Sr |-id=Rubidium-95m | style="text-indent:1em" | 95mRb | colspan="3" style="text-indent:2em" | 835.0(6) keV | style="text-align:center" | 2009 | <500 ns | IT | 95Rb | 9/2+#
|-id=Rubidium-96 | rowspan=2|96Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 59 | rowspan=2|95.9341334(36) | rowspan=2 style="text-align:center" | 1967 | rowspan=2|201.5(9) ms | β− (86.3%) | 96Sr | rowspan=2|2− | rowspan=2| | rowspan=2| |- | β−, n (13.7%) | 95Sr |-id=Rubidium-96m1 | style="text-indent:1em" | 96m1RbOrder of ground state and isomer is uncertain. | colspan="3" style="text-indent:2em" | 0(200)# keV | style="text-align:center" | (1981)Half-life not measured, only circumstantial evidence for the isomeric state | 200# ms[>1 ms]
| 1(+#)
|-id=Rubidium-96m2 | style="text-indent:1em" | 96m2Rb | colspan="3" style="text-indent:2em" | 1134.6(11) keV | style="text-align:center" | 1999 | 1.80(4) μs | IT | 96Rb | (10−)
|-id=Rubidium-97 | rowspan=2|97Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 60 | rowspan=2|96.9371771(21) | rowspan=2 style="text-align:center" | 1969 | rowspan=2|169.1(6) ms | β− (74.5%) | 97Sr | rowspan=2|3/2+ | rowspan=2| | rowspan=2| |- | β−, n (25.5%) | 96Sr |-id=Rubidium-97m | style="text-indent:1em" | 97mRb | colspan="3" style="text-indent:2em" | 76.6(2) keV | style="text-align:center" | 2012 | 5.7(6) μs | IT | 97Rb | (1/2,3/2)−
|-id=Rubidium-98 | rowspan=3|98Rb | rowspan=3 style="text-align:right" | 37 | rowspan=3 style="text-align:right" | 61 | rowspan=3|97.941632(17) | rowspan=3 style="text-align:center" | 1971 | rowspan=3|115(6) ms | β−(85.65%) | 98Sr | rowspan=3|(0−) | rowspan=3| | rowspan=3| |- | β−, n (14.3%) | 97Sr |- | β−, 2n (0.054%) | 96Sr |-id=Rubidium-98m1 | style="text-indent:1em" | 98m1Rb | colspan="3" style="text-indent:2em" | 73(26) keV | style="text-align:center" | 1980 | 96(3) ms | β− | 98Sr | (3+)
|-id=Rubidium-98m2 | style="text-indent:1em" | 98m2Rb | colspan="3" style="text-indent:2em" | 178.5(4) keV | style="text-align:center" | 2009 | 358(7) ns | IT | 98Rb | (2−)
|-id=Rubidium-99 | rowspan=2|99Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 62 | rowspan=2|98.9451192(43) | rowspan=2 style="text-align:center" | 1971 | rowspan=2|54(4) ms | β− (82.7%) | 99Sr | rowspan=2|(3/2+) | rowspan=2| | rowspan=2| |- | β−, n (17.3%) | 98Sr |-id=Rubidium-100 | rowspan=3|100Rb | rowspan=3 style="text-align:right" | 37 | rowspan=3 style="text-align:right" | 63 | rowspan=3|99.950332(14) | rowspan=3 style="text-align:center" | 1978 | rowspan=3|51.3(16) ms | β− (94.3%) | 100Sr | rowspan=3|4−# | rowspan=3| | rowspan=3| |- | β−, n (5.6%) | 99Sr |- | β−, 2n (0.15%) | 98Sr |-id=Rubidium-101 | rowspan=2|101Rb