Naturally occurring cadmium () is composed of 8 isotopes. For two of them, natural radioactivity has been observed, and three others are predicted to possibly decay though this has not been observed; it may be presumed the half-lives are extremely long. The two natural radioactive isotopes are (beta decay, half-life ) and (double beta decay, half-life ). The other three are , (double electron capture), and (double beta decay); only lower limits on their decays have been set. Only three isotopes—, , and —are theoretically stable. Among the isotopes absent in natural cadmium, the most long-lived are with a half-life of 461.3 days, and with a half-life of 53.46 hours. All of the remaining radioactive isotopes have half-lives that are less than 7 hours and the majority of these are less than 5 minutes. This element also has 12 known meta states, with the most stable being ( 13.9 years), ( 44.6 days) and ( 3.44 hours).
The known isotopes of cadmium range from to . The primary decay mode before the stable isotope is electron capture to isotopes of silver, and after, beta emission to isotopes of indium.
A 2021 study has shown at high ionic strengths, cadmium isotope fractionation mainly depends on its complexation with carboxylic sites. At low ionic strengths, nonspecific cadmium binding induced by electrostatic attractions plays a dominant role and promotes cadmium isotope fractionation during complexation.
List of isotopes
|-id=Cadmium-94 | | style="text-align:right" | 48 | style="text-align:right" | 46 | 93.95659(54)# | style="text-align:center" | 2016 | 80# ms[> 760 ns]
| 0+
|-id=Cadmium-95 | rowspan=2| | rowspan=2 style="text-align:right" | 48 | rowspan=2 style="text-align:right" | 47 | rowspan=2|94.94948(61)# | rowspan=2 style="text-align:center" | 2012 | rowspan=2|32(3) ms | β+ (95.4%) | | rowspan=2|9/2+# | rowspan=2| | rowspan=2| |- | β+, p (4.6%) | |-id=Cadmium-96 | rowspan=2| | rowspan=2 style="text-align:right" | 48 | rowspan=2 style="text-align:right" | 48 | rowspan=2|95.94034(44)# | rowspan=2 style="text-align:center" | 2008 | rowspan=2|1.003(47) s | β+ (98.4%) | | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β+, p (1.6%) | |-id=Cadmium-96m1 | rowspan=2 style="text-indent:1em" | | rowspan=2 colspan="3" style="text-indent:2em" | 6000(1400) keV | rowspan=2 style="text-align:center" | 2019 | rowspan=2|511(26) ms | β+ (84.6%) | | rowspan=2|16+ | rowspan=2| | rowspan=2| |- | β+, p (15.4%) | |-id=Cadmium-96m2 | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 5605(5) keV | style="text-align:center" | 2011 | 198(18) ns | IT | | (12−,13−)
|-id=Cadmium-97 | rowspan=2| | rowspan=2 style="text-align:right" | 48 | rowspan=2 style="text-align:right" | 49 | rowspan=2|96.93480(45) | rowspan=2 style="text-align:center" | 1978 | rowspan=2|1.16(5) s | β+ (92.6%) | | rowspan=2|(9/2+) | rowspan=2| | rowspan=2| |- | β+, p (7.4%) | |-id=Cadmium-97m1 | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 1245.1(2) keV | style="text-align:center" | 2019 | 730(70) μs | IT | | (1/2−)
|-id=Cadmium-97m2 | rowspan=2 style="text-indent:1em" | | rowspan=2 colspan="3" style="text-indent:2em" | 2620(580) keV | rowspan=2 style="text-align:center" | 2011 | rowspan=2|3.86(6) s | β+ (74.9%) | | rowspan=2|(25/2+) | rowspan=2| | rowspan=2| |- | β+, p (25.1%) | |-id=Cadmium-98 | rowspan=2| | rowspan=2 style="text-align:right" | 48 | rowspan=2 style="text-align:right" | 50 | rowspan=2|97.927389(56) | rowspan=2 style="text-align:center" | 1978 | rowspan=2|9.29(10) s | β+ (>99.97%) | | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β+, p (<0.029%) | |-id=Cadmium-98m1 | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 2428.3(4) keV | style="text-align:center" | 1997 | 154(16) ns | IT | | (8+)
|-id=Cadmium-98m2 | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 6635(2) keV | style="text-align:center" | 2004 | 224(5) ns | IT | | (12+)
|-id=Cadmium-99 | rowspan=3| | rowspan=3 style="text-align:right" | 48 | rowspan=3 style="text-align:right" | 51 | rowspan=3|98.9249258(17) | rowspan=3 style="text-align:center" | 1978 | rowspan=3|17(1) s | β+ (99.79%) | | rowspan=3|5/2+# | rowspan=3| | rowspan=3| |- | β+, p (0.21%)
| β+, α (<10−4%) | |-id=Cadmium-100 | | style="text-align:right" | 48 | style="text-align:right" | 52 | 99.9203488(18) | style="text-align:center" | 1970 | 49.1(5) s | β+ | | 0+
|-id=Cadmium-101 | | style="text-align:right" | 48 | style="text-align:right" | 53 | 100.9185862(16) | style="text-align:center" | 1969 | 1.36(5) min | β+ | | 5/2+
|-id=Cadmium-102 | | style="text-align:right" | 48 | style="text-align:right" | 54 | 101.9144818(18) | style="text-align:center" | 1969 | 5.5(5) min | β+ | | 0+
|-id=Cadmium-103 | | style="text-align:right" | 48 | style="text-align:right" | 55 | 102.9134169(19) | style="text-align:center" | 1960 | 7.3(1) min | β+ | | 5/2+
|-id=Cadmium-104 | | style="text-align:right" | 48 | style="text-align:right" | 56 | 103.9098562(18) | style="text-align:center" | 1955 | 57.7(10) min | β+ | | 0+
|-id=Cadmium-105 | | style="text-align:right" | 48 | style="text-align:right" | 57 | 104.9094639(15) | style="text-align:center" | 1950 | 55.5(4) min | β+ | | 5/2+
|-id=Cadmium-105m | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 2517.6(5) keV | style="text-align:center" | 1978 | 4.5(5) μs | IT | | (21/2+)
|-id=Cadmium-106 | | style="text-align:right" | 48 | style="text-align:right" | 58 | 105.9064598(12) | style="text-align:center" | 1934 | colspan=3 align=center|Observationally stableBelieved to decay by β+β+ to with a half-life over 1.1×1021 years | 0+ | 0.01245(22) | |-id=Cadmium-107 | | style="text-align:right" | 48 | style="text-align:right" | 59 | 106.9066120(18) | style="text-align:center" | 1946 | 6.50(2) h | β+ | | 5/2+
|-id=Cadmium-108 | | style="text-align:right" | 48 | style="text-align:right" | 60 | 107.9041836(12) | style="text-align:center" | 1934 | colspan=3 align=center|Observationally stableBelieved to decay by β+β+ to with a half-life over 4.1×1017 years | 0+ | 0.00888(11) | |-id=Cadmium-109 | | style="text-align:right" | 48 | style="text-align:right" | 61 | 108.9049867(16) | style="text-align:center" | 1950 | 461.3(5) d | EC | | 5/2+
|-id=Cadmium-109m1 | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 59.60(7) keV | style="text-align:center" | 1964 | 11.8(16) μs | IT | | 1/2+
|-id=Cadmium-109m2 | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 463.10(11) keV | style="text-align:center" | 1966 | 10.6(4) μs | IT | | 11/2−
|-id=Cadmium-110 | | style="text-align:right" | 48 | style="text-align:right" | 62 | 109.90300747(41) | style="text-align:center" | 1924 | colspan=3 align=center|Stable | 0+ | 0.12470(61) | |-id=Cadmium-111 | Fission product | style="text-align:right" | 48 | style="text-align:right" | 63 | 110.90418378(38) | style="text-align:center" | 1924 | colspan=3 align=center|Stable | 1/2+ | 0.12795(12) | |-id=Cadmium-111m | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 396.214(21) keV | style="text-align:center" | 1951 | 48.50(9) min | IT | | 11/2−
|-id=Cadmium-112 | | style="text-align:right" | 48 | style="text-align:right" | 64 | 111.90276390(27) | style="text-align:center" | 1924 | colspan=3 align=center|Stable | 0+ | 0.24109(7) | |-id=Cadmium-113 | Primordial radionuclide | style="text-align:right" | 48 | style="text-align:right" | 65 | 112.90440811(26) | style="text-align:center" | 1924 | 8.04(5)×1015 y | β− | | 1/2+ | 0.12227(7) | |-id=Cadmium-113m | rowspan=2 style="text-indent:1em" | | rowspan=2 colspan="3" style="text-indent:2em" | 263.54(3) keV | rowspan=2 style="text-align:center" | 1959 | rowspan=2|13.89(11) y | β− (99.90%) | | rowspan=2|11/2− | rowspan=2| | rowspan=2| |- | IT (0.0964%) | |-id=Cadmium-114 | | style="text-align:right" | 48 | style="text-align:right" | 66 | 113.90336500(30) | style="text-align:center" | 1924 | colspan=3 align=center|Observationally stableBelieved to undergo β−β− decay to with a half-life over 9.2×1016 years | 0+ | 0.28754(81) | |-id=Cadmium-115 | rowspan=2 | | rowspan=2 style="text-align:right" | 48 | rowspan=2 style="text-align:right" | 67 | rowspan=2 |114.90543743(70) | rowspan=2 style="text-align:center" | 1939 | rowspan=2 |53.46(5) h | β− | | rowspan=2 |1/2+ | rowspan=2 | | rowspan=2 | |- | β− (8.0×10−5%) | |-id=Cadmium-115m | rowspan=2 style="text-indent:1em" | | rowspan=2 colspan="3" style="text-indent:2em" | 181.0(5) keV | rowspan=2 style="text-align:center" | 1947 | rowspan=2 |44.56(24) d | β− (98.3%) | | rowspan=2 |11/2− | rowspan=2 | | rowspan=2 | |- | β− (1.7%) | |-id=Cadmium-116 | | style="text-align:right" | 48 | style="text-align:right" | 68 | 115.90476323(17) | style="text-align:center" | 1924 | 2.69(9)×1019 y | β−β− | | 0+ | 0.07512(54) | |-id=Cadmium-117 | | style="text-align:right" | 48 | style="text-align:right" | 69 | 116.9072260(11) | style="text-align:center" | 1939 | 2.503(5) h | β− | | 1/2+
|-id=Cadmium-117m | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 136.4(2) keV | style="text-align:center" | 1966 | 3.441(9) h | β− | | 11/2−
|-id=Cadmium-118 | | style="text-align:right" | 48 | style="text-align:right" | 70 | 117.906922(21) | style="text-align:center" | 1961 | 50.3(2) min | β− | | 0+
|-id=Cadmium-119 | | style="text-align:right" | 48 | style="text-align:right" | 71 | 118.909847(40) | style="text-align:center" | 1961 | 2.69(2) min | β− | | 1/2+
|-id=Cadmium-119m | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 146.54(11) keV | style="text-align:center" | 1974 | 2.20(2) min | β− | | 11/2−
|-id=Cadmium-120 | | style="text-align:right" | 48 | style="text-align:right" | 72 | 119.9098681(40) | style="text-align:center" | 1971 | 50.80(21) s | β− | | 0+
|-id=Cadmium-121 | | style="text-align:right" | 48 | style="text-align:right" | 73 | 120.9129637(21) | style="text-align:center" | 1965 | 13.5(3) s | β− | | 3/2+
|-id=Cadmium-121m | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 214.86(15) keV | style="text-align:center" | 1974 | 8.3(8) s | β− | | 11/2−
|-id=Cadmium-122 | | style="text-align:right" | 48 | style="text-align:right" | 74 | 121.9134591(25) | style="text-align:center" | 1973 | 5.98(10) s | β− | | 0+
|-id=Cadmium-123 | | style="text-align:right" | 48 | style="text-align:right" | 75 | 122.9168925(29) | style="text-align:center" | 1983 | 2.10(2) s | β− | | 3/2+
|-id=Cadmium-123m | rowspan=2 style="text-indent:1em" | | rowspan=2 colspan="3" style="text-indent:2em" | 143(4) keV | rowspan=2 style="text-align:center" | 1986 | rowspan=2|1.82(3) s | β− (?%) | | rowspan=2|11/2− | rowspan=2| | rowspan=2| |- | IT (?%) | |-id=Cadmium-124 | | style="text-align:right" | 48 | style="text-align:right" | 76 | 123.9176598(28) | style="text-align:center" | 1974 | 1.25(2) s | β− | | 0+
|-id=Cadmium-125 | | style="text-align:right" | 48 | style="text-align:right" | 77 | 124.9212576(31) | style="text-align:center" | 1986 | 680(40) ms | β− | | 3/2+
|-id=Cadmium-125m1 | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 186(4) keV | style="text-align:center" | 1989 | 480(30) ms | β− | | 11/2−
|-id=Cadmium-125m2 | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 1648(4) keV | style="text-align:center" | 2012 | 19(3) μs | IT | | (19/2+)
|-id=Cadmium-126 | | style="text-align:right" | 48 | style="text-align:right" | 78 | 125.9224303(25) | style="text-align:center" | 1978 | 512(5) ms | β− | | 0+
|-id=Cadmium-127 | | style="text-align:right" | 48 | style="text-align:right" | 79 | 126.9262033(67) | style="text-align:center" | 1986 | 480(100) ms | β− | | 3/2+
|-id=Cadmium-127m1 | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | 285(8) keV | style="text-align:center" | 2013 | 360(40) ms | β− | | 11/2−
|-id=Cadmium-127m2