Gold (79Au) has one stable isotope, 197Au, and known radioisotopes ranging from 169Au to 210Au, with 195Au being the most stable with a half-life of 186.01 days, followed by 196Au at 6.165 days. Isotopes heavier than the stable mass number 197 generally decay by beta emission to mercury isotopes, while those lighter decay by electron capture to platinum isotopes or alpha emission to iridium isotopes; 196 decays both to platinum and to mercury. Of the meta states the most stable is 198m2Au at 2.27 days.
Gold is currently the heaviest monoisotopic element (and is also mononuclidic). Bismuth formerly held that distinction until alpha decay of the 209Bi isotope was observed. All isotopes of gold are either radioactive or, in the case of 197Au, observationally stable, meaning that 197Au is predicted to be radioactive but no actual decay has been observed.
List of isotopes
|-id=Gold-169 | rowspan=2|169Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 90 | rowspan=2| 168.99808(32)# | rowspan=2 style="text-align:center" | (2000) | rowspan=2 data-sort-value="1.16e-6"| | p (~94%) | 168Pt | rowspan=2|(11/2−) | rowspan=2| |- | α (~6%) | 165mIr |-id=Gold-170 | rowspan=2|170Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 91 | rowspan=2|169.99602(22)# | rowspan=2 style="text-align:center" | 2004 | rowspan=2 data-sort-value="286.0e-6"| | p (89%) | 169Pt | rowspan=2|(2)− | rowspan=2| |- | α (11%) | 166Ir |-id=Gold-170m | rowspan=2 style="text-indent:1em" | 170mAu | rowspan=2 colspan="3" style="text-indent:2em" | 282(10) keV | rowspan=2 style="text-align:center" | 2004 | rowspan=2 data-sort-value="617.0e-6"| | p (58%) | 169Pt | rowspan=2|(9)+ | rowspan=2| |- | α (42%) | 166mIr |-id=Gold-171 | rowspan=2|171Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 92 | rowspan=2|170.991882(22) | rowspan=2 data-sort-value="22.0e-6" style="text-align:center" | 1997 | rowspan=2 data-sort-value="22.0e-6"| | p | 170Pt | rowspan=2|1/2+ | rowspan=2| |- | α? | 167Ir |-id=Gold-171m | rowspan=2 style="text-indent:1em" | 171mAu | rowspan=2 colspan="3" style="text-indent:2em" | 258(13) keV | rowspan=2 data-sort-value="1.09e-3" style="text-align:center" | 1999 | rowspan=2 data-sort-value="1.09e-3"|1.09(3) ms | α (66%) | 167mIr | rowspan=2|11/2− | rowspan=2| |- | p (34%) | 170Pt |-id=Gold-172 | rowspan=3|172Au | rowspan=3 style="text-align:right" | 79 | rowspan=3 style="text-align:right" | 93 | rowspan=3|171.99000(6) | rowspan=3 data-sort-value="28.0e-3" style="text-align:center" | 1993 | rowspan=3 data-sort-value="28.0e-3"|28(4) ms | α (98%) | 168Ir | rowspan=3|(2)− | rowspan=3| |- | p (2%) | 171Pt |- | β+ | 172Pt |-id=Gold-172m | rowspan=2 style="text-indent:1em" | 172mAuOrder of ground state and isomer is uncertain. | rowspan=2 colspan="3" style="text-indent:2em" | 160(250) keV | rowspan=2 data-sort-value="11.0e-3" style="text-align:center" | 2009 | rowspan=2 data-sort-value="11.0e-3"|11.0(10) ms | α | 168Ir | rowspan=2|(9,10)+ | rowspan=2| |- | p? | 171Pt |-id=Gold-173 | rowspan=2|173Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 94 | rowspan=2|172.986224(24) | rowspan=2 data-sort-value="25.5e-3" style="text-align:center" | 1983 | rowspan=2 data-sort-value="25.5e-3"|25.5(8) ms | α (86%) | 169Ir | rowspan=2|(1/2+) | rowspan=2| |- | β+ (14%) | 173Pt |-id=Gold-173m | rowspan=2 style="text-indent:1em" | 173mAu | rowspan=2 colspan="3" style="text-indent:2em" | 214(21) keV | rowspan=2 data-sort-value="12.2e-3" style="text-align:center" | 1999 | rowspan=2 data-sort-value="12.2e-3"|12.2(1) ms | α (89%) | 169Ir | rowspan=2|(11/2−) | rowspan=2| |- | β+ (11%) | 173Pt |-id=Gold-174 | rowspan=2|174Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 95 | rowspan=2|173.98491(11)# | rowspan=2 data-sort-value="139.0e-3" style="text-align:center" | 1983 | rowspan=2 data-sort-value="139.0e-3"|139(3) ms | α (90%) | 170Ir | rowspan=2|(3−) | rowspan=2| |- | β+ (10%) | 174Pt |-id=Gold-174m | rowspan=2 style="text-indent:1em" | 174mAu | rowspan=2 colspan="3" style="text-indent:2em" | 130(50)# keV | rowspan=2 style="text-align:center" | (2004) Only published in a conference proceeding and not a refereed journal | rowspan=2 data-sort-value="162.0e-3"|162(2) ms | α? | 170Ir | rowspan=2|(9+) | rowspan=2| |- | β+? | 174Pt |-id=Gold-175 | rowspan=2|175Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 96 | rowspan=2|174.98132(4) | rowspan=2 data-sort-value="200.0e-3" style="text-align:center" | 1975 | rowspan=2 data-sort-value="200.0e-3"|200(3) ms | α (88%) | 171Ir | rowspan=2|1/2+ | rowspan=2| |- | β+ (12%) | 175Pt |-id=Gold-175m | rowspan=2 style="text-indent:1em" | 175mAu | rowspan=2 colspan="3" style="text-indent:2em" | 164(11)# keV | rowspan=2 data-sort-value="136.0e-3" style="text-align:center" | 2013 | rowspan=2 data-sort-value="136.0e-3"|136(1) ms | α (75%) | 171Ir | rowspan=2|(11/2−) | rowspan=2| |- | β+ (25%) | 175Pt |-id=Gold-176 | rowspan=2|176Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 97 | rowspan=2|175.98012(4) | rowspan=2 data-sort-value="1.05" style="text-align:center" | 1975 | rowspan=2 data-sort-value="1.05"|1.05(1) s | α (75%) | 172Ir | rowspan=2|(3−,4−) | rowspan=2| |- | β+ (25%) | 176Pt |-id=Gold-176m | rowspan=2 style="text-indent:1em" | 176mAu | rowspan=2 colspan="3" style="text-indent:2em" | 139(13) keV | rowspan=2 data-sort-value="1.36" style="text-align:center" | 2014 | rowspan=2 data-sort-value="1.36"|1.36(2) s | α? | 172Ir | rowspan=2|(8+,9+) | rowspan=2| |- | β+? | 176Pt |-id=Gold-177 | rowspan=2|177Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 98 | rowspan=2|176.976870(11) | rowspan=2 data-sort-value="1.501" style="text-align:center" | 1968 | rowspan=2 data-sort-value="1.501"|1.501(20) s | β+ (60%) | 177Pt | rowspan=2|1/2+ | rowspan=2| |- | α (40%) | 173Ir |-id=Gold-177m | rowspan=2 style="text-indent:1em" | 177mAu | rowspan=2 colspan="3" style="text-indent:2em" | 190(7) keV | rowspan=2 data-sort-value="1.193" style="text-align:center" | 2001 | rowspan=2 data-sort-value="1.193"|1.193(13) s | α (60%) | 173Ir | rowspan=2|11/2− | rowspan=2| |- | β+ (40%) | 177Pt |-id=Gold-178 | rowspan=2|178Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 99 | rowspan=2|177.976057(11) | rowspan=2 data-sort-value="3.4" style="text-align:center" | 1968 | rowspan=2 data-sort-value="3.4"|3.4(5) s | β+ (84%) | 178Pt | rowspan=2|(2+,3−) | rowspan=2| |- | α (16%) | 174Ir |-id=Gold-178m1 | style="text-indent:1em" | 178m1Au | colspan="3" style="text-indent:2em" | 50.3(2) keV | style="text-align:center" | 2021 | data-sort-value="300.0e-9"| 300(10) ns | IT | 178Au | (4−,5+) | |-id=Gold-178m2 | rowspan=2 style="text-indent:1em" | 178m2Au | rowspan=2 colspan="3" style="text-indent:2em" | 186(14) keV | rowspan=2 data-sort-value="2.7" style="text-align:center" | 2020 | rowspan=2 data-sort-value="2.7"|2.7(5) s | β+ (82%) | 178Pt | rowspan=2|(7+,8−) | rowspan=2| |- | α (18%) | 174Ir |-id=Gold-178m3 | style="text-indent:1em" | 178m3Au | colspan="3" style="text-indent:2em" | 243(14) keV | style="text-align:center" | 2021 | data-sort-value="390.0e-9"| 390(10) ns | IT | 178Au | (5+,6) | |-id=Gold-179 | rowspan=2|179Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 100 | rowspan=2|178.973174(13) | rowspan=2 style="text-align:center" | 1968 | rowspan=2|7.1(3) s | β+ (78.0%) | 179Pt | rowspan=2|1/2+ | rowspan=2| |- | α (22.0%) | 175Ir |-id=Gold-179m1 | style="text-indent:1em" | 179m1Au | colspan="3" style="text-indent:2em" | 89.5(3) keV | style="text-align:center" | 2011 | data-sort-value="327.0e-9"| 327(5) ns | IT | 179Au | (3/2−) | |-id=Gold-179m2 | style="text-indent:1em" | 179m2Au | colspan="3" style="text-indent:2em" | 1743(17) keV | style="text-align:center" | 2011 | data-sort-value="2.16e-6"| 2.16(8) μs | IT | 179Au | (19/2+) | |-id=Gold-180 | rowspan=2|180Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 101 | rowspan=2|179.9724898(51) | rowspan=2 style="text-align:center" | 1977 | rowspan=2|7.9(3) s | β+ (99.42%) | 180Pt | rowspan=2|(1+) | rowspan=2| |- | α (0.58%) | 176Ir |-id=Gold-181 | rowspan=2|181Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 102 | rowspan=2|180.970079(21) | rowspan=2 style="text-align:center" | 1968 | rowspan=2|13.7(14) s | β+ (97.3%) | 181Pt | rowspan=2|(5/2−) | rowspan=2| |- | α (2.7%) | 177Ir |-id=Gold-182 | rowspan=2|182Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 103 | rowspan=2|181.969614(20) | rowspan=2 style="text-align:center" | 1970 | rowspan=2|15.5(4) s | β+ (99.87%) | 182Pt | rowspan=2|(2+) | rowspan=2| |- | α (0.13%) | 178Ir |-id=Gold-183 | rowspan=2|183Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 104 | rowspan=2|182.967588(10) | rowspan=2 style="text-align:center" | 1968 | rowspan=2|42.8(10) s | β+ (99.45%) | 183Pt | rowspan=2|5/2− | rowspan=2| |- | α (0.55%) | 179Ir |-id=Gold-183m | style="text-indent:1em" | 183mAu | colspan="3" style="text-indent:2em" | 73.10(1) keV | style="text-align:center" | 1984 | data-sort-value="1.000001e-6"| >1 μs | IT | 183Au | (1/2)+ | |-id=Gold-184 | rowspan=2|184Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 105 | rowspan=2|183.967452(24) | rowspan=2 style="text-align:center" | 1969 | rowspan=2|20.6(9) s | β+ (99.99%) | 184Pt | rowspan=2|5+ | rowspan=2| |- | α (0.013%) | 180Ir |-id=Gold-184m | rowspan=3 style="text-indent:1em" | 184mAu | rowspan=3 colspan="3" style="text-indent:2em" | 68.46(4) keV | rowspan=3 style="text-align:center" | 1997 | rowspan=3|47.6(14) s | β+ (70%) | 184Pt | rowspan=3|2+ | rowspan=3| |- | IT (30%) | 184Au |- | α (0.013%) | 180Ir |-id=Gold-185 | rowspan=2|185Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 106 | rowspan=2|184.9657989(28) | rowspan=2 data-sort-value="255.0" style="text-align:center" | 1960 | rowspan=2 data-sort-value="255.0"| 4.25(6) min | β+ (99.74%) | 185Pt | rowspan=2|5/2− | rowspan=2| |- | α (0.26%) | 181Ir |-id=Gold-185m1 | rowspan=2 style="text-indent:1em" | 185m1Au | rowspan=2 colspan="3" style="text-indent:2em" | 50(50)# keV | rowspan=2 data-sort-value="408.0" style="text-align:center" | 1968 | rowspan=2 data-sort-value="408.0"|6.8(3) min | β+ | 185Pt | rowspan=2|1/2+# | rowspan=2| |- | IT? | 185Au |-id=Gold-185m2 | style="text-indent:1em" | 185m2Au | colspan="3" style="text-indent:2em" | 1504.2(4)# keV | data-sort-value="408.0" style="text-align:center" | 1968 | data-sort-value="630e-9"| 630(80) ns | IT | 185Au
|-id=Gold-186 | rowspan=2|186Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 107 | rowspan=2|185.965953(23) | rowspan=2 data-sort-value="642.0" style="text-align:center" | 1960 | rowspan=2 data-sort-value="642.0"|10.7(5) min | β+ | 186Pt | rowspan=2|3− | rowspan=2| |- | α (8×10−4%) | 182Ir |-id=Gold-186m | style="text-indent:1em" | 186mAu | colspan="3" style="text-indent:2em" | 227.77(7) keV | style="text-align:center" | 1985 | data-sort-value="110.0e-9"| 110(10) ns | IT | 186Au | 2+ | |-id=Gold-187 | rowspan=2|187Au | rowspan=2 style="text-align:right" | 79 | rowspan=2 style="text-align:right" | 108 | rowspan=2|186.964542(24) | rowspan=2 data-sort-value="498.0" style="text-align:center" | 1955 | rowspan=2 data-sort-value="498.0"|8.3(2) min | β+ | 187Pt | rowspan=2|1/2+ | rowspan=2| |- | α? | 183Ir |-id=Gold-187m1 | style="text-indent:1em" | 187m1Au | colspan="3" style="text-indent:2em" | 120.33(14) keV | style="text-align:center" | 1983 | 2.3(1) s | IT | 187Au | 9/2− | |-id=Gold-187m2 | style="text-indent:1em" | 187m2Au | colspan="3" style="text-indent:2em" | 2669.4(18) keV | style="text-align:center" | 1989