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Half Lives

The half-life of a radioactive element is the time that it takes for one half of the atoms of that substance to disintegrate into another nuclear form. These can range from mere fractions of a second, to many billions of years. In addition, the half-life of a particular radionuclide is unique to that radionuclide, meaning that knowledge of the half-life leads to the identity of the radionuclide. The following is a listing of the half-lives of commonly-encountered radionuclides, with the units of each as shown.

Please note that some of the longer half-lives are written in scientific notation (i.e., 7.2E1 is equal to 7.2 x 10, or 72.)

Actinium

  • Ac-225 – 10.0 days
  • Ac-227 – 21.773 years
  • Ac-228 – 6.13 hours

Americium

  • Am-241 – 432.2 years
  • Am-242 – 16.02 hours
  • Am-242m – 152 years
  • Am-243 – 7380 years

Antimony

  • Sb-124 – 60.20 days
  • Sb-125 – 2.77 years
  • Sb-126 – 12.4 days
  • Sb-126m – 19.0 minutes
  • Sb-127 – 3.85 days

Argon

  • Ar-41 – 1.827 hours

Astatine

  • At-217 – 0.0323 seconds
  • At-218 – 2 seconds

Barium

  • Ba-137m – 2.552 minutes
  • Ba-139 – 82.7 minutes
  • Ba-140 – 12.74 days
  • Ba-141 – 18.27 minutes
  • Ba-142 – 10.6 minutes

Beryllium

  • Be-10 – 1.6E6 years
  • Be-7 – 53.44 days

Bismuth

  • Bi-210 – 5.012 days
  • Bi-211 – 2.14 minutes
  • Bi-212 – 60.55 minutes
  • Bi-213 – 45.65 minutes
  • Bi-214 – 19.9 minutes

Bromine

  • Br-82 – 35.30 hours
  • Br-83 – 2.39 hours
  • Br-84 – 31.80 minutes

Cadmium

  • Cd-113m – 13.6 years
  • Cd-115m – 44.6 days

Calcium

  • Ca-41 – 1.3E5 years
  • Ca-47 – 4.53 days

Californium

  • Cf-252 – 2.638 years

Carbon

  • C-11 – 20.38 minutes
  • C-14 – 5730 years

Cerium

  • Ce-141 – 32.50 days
  • Ce-143 – 33.0 hours
  • Ce-144 – 284.3 days

Cesium

  • Cs-134 – 2.062 years
  • Cs-134m – 2.90 hours
  • Cs-135 – 2.3E6 years
  • Cs-136 – 13.1 days
  • Cs-137 – 30.0 years
  • Cs-138 – 32.2 minutes

Chromium

  • Cr-51 – 27.704 days

Cobalt

  • Co-56 – 78.76 days
  • Co-57 – 270.9 days
  • Co-58 – 70.8 days
  • Co-60 – 5.27 years

Copper

  • Cu-61 – 3.408 hours
  • Cu-64 – 12.701 hours

Curium

  • Cm-242 – 162.8 days
  • Cm-243 – 28.5 years
  • Cm-244 – 18.11 years
  • Cm-245 – 8500 years
  • Cm-246 – 4730 years
  • Cm-247 – 1.56E7 years
  • Cm-248 – 3.39E5 years

Europium

  • Eu-152 – 13.33 years
  • Eu-154 – 8.8 years
  • Eu-155 – 4.96 years
  • Eu-156 – 15.19 days

Fluorine

  • F-18 – 109.74 minutes

Francium

  • Fr-221 – 4.8 minutes
  • Fr-223 – 21.8 minutes

Gadolinium

  • Gd-152 – 1.08E14 years

Gallium

  • Ga-67 – 3.261 days

Gold

  • Au-198 – 2.696 days

Holmium

  • Ho-166m – 1.20E3 years

Hydrogen

  • H-3 – 12.35 years

Indium

  • In-111 – 2.83 days
  • In-113 – 1.658 hours
  • In-115 – 5.1E15 years

Iodine

  • I-123 – 13.2 hours
  • I-125 – 60.14 days
  • I-129 – 1.57E7 years
  • I-130 – 12.36 hours
  • I-131 – 8.04 days
  • I-132 – 2.30 hours
  • I-133 – 20.8 hours
  • I-134 – 52.6 minutes
  • I-135 – 6.61 hours

Iridium

  • Ir-192 – 74.02 days

Iron

  • Fe-55 – 2.7 years
  • Fe-59 – 44.53 days

Krypton

  • Kr-83m – 1.83 hours
  • Kr-85 – 10.72 years
  • Kr-85m – 4.48 hours
  • Kr-87 – 76.3 minutes
  • Kr-88 – 2.84 minutes

Lanthanum

  • La-140 – 40.272 hours
  • La-141 – 3.93 hours
  • La-142 – 92.5 minutes

Lead

  • Pb-209 – 3.253 hours
  • Pb-210 – 22.3 years
  • Pb-211 – 36.1 minutes
  • Pb-212 – 10.64 hours
  • Pb-214 – 26.8 minutes
  • Pb-214 – 26.8 minutes

Manganese

  • Mn-52 – 5.591 days
  • Mn-52m – 21.1 minutes
  • Mn-54 – 312.5 days
  • Mn-56 – 2.579 hours
  • Mn-57 – 36.08 hours

Mercury

  • Hg-197 – 64.1 hours
  • Hg-203 – 46.60 days

Molybdenum

  • Mo-93 – 3.5E3 years
  • Mo-99 – 66.0 hours

Neodymium

  • Nd-147 – 10.98 days

Neptunium

  • Np-237 – 2.14E6 years
  • Np-238 – 2.117 days
  • Np-239 – 2.355 days
  • Np-240 – 65 minutes
  • Np-240m – 7.4 minutes

Nickel

  • Ni-59 – 7.5E4 years
  • Ni-63 – 96 years
  • Ni-65 – 2.520 hours

Niobium

  • Nb-93m – 13.6 years
  • Nb-95 – 35.15 days
  • Nb-95m – 86.6 hours
  • Nb-97 – 72.1 minutes
  • Nb-97m – 60 seconds

Nitrogen

  • N-13 – 9.97 minutes
  • N-16 – 7.13 seconds

Oxygen

  • O-15 – 122.24 seconds

Palladium

  • Pd-107 – 6.5E6 years
  • Pd-109 0- 13.427 hours

Phosphorus

  • P-32 – 14.29 days

Plutonium

  • Pu-238 – 87.74 years
  • Pu-239 – 24065 years
  • Pu-240 – 6537 years
  • Pu-241 – 14.4 years
  • Pu-242 – 3.76E5 years
  • Pu-243 – 4.956 hours
  • Pu-244 – 8.26E7 years

Polonium

  • Po-210 – 138.38 days
  • Po-211 – 0.516 seconds
  • Po-212 – 0.305 microseconds
  • Po-213 – 4.2 microseconds
  • Po-214 – 164.3 microseconds
  • Po-215 – 0.00178 seconds
  • Po-216 – 0.15 seconds
  • Po-218 – 3.05 minutes

Potassium

  • K-40 – 1.27E9 years
  • K-42 – 12.36 hours
  • K-43 – 22.6 hours

Praseodymium

  • Pr-143 – 13.56 days
  • Pr-144 – 17.28 minutes
  • Pr-144m – 7.2 minutes

Promethium

  • Pm-147 – 2.6234 years
  • Pm-148 – 5.37 days
  • Pm-148 – 41.3 days
  • Pm-149 – 53.08 hours
  • Pm-151 – 28.40 hours

Protactinium

  • Pa-231 – 3.28E4 years
  • Pa-233 – 27.0 days
  • Pa-234 – 6.70 hours
  • Pa-234m – 1.17 minutes

Radium

  • Ra-223 – 11.434 days
  • Ra-224 – 3.66 days
  • Ra-225 – 14.8 days
  • Ra-226 – 1600 years
  • Ra-228 – 5.75 years

Radon

  • Rn-219 – 3.96 seconds
  • Rn-220 – 55.6 seconds
  • Rn-222 – 3.824 days

Rhenium

  • Re-187 – 5E10 years

Rhodium

  • Rh-103m – 56.12 minutes
  • Rh-105 – 35.36 hours
  • Rh-106 – 29.9 seconds

Rubidium

  • Rb-86 – 18.66 days
  • Rb-87 – 4.7E10 years
  • Rb-88 – 17.8 minutes
  • Rb-89 – 15.2 minutes

Ruthenium

  • Ru-103 – 39.28 days
  • Ru-105 – 4.44 hours
  • Ru-106 – 368.2 days
  • Ru-97 – 2.9 days

Samarium

  • Sm-147 – 1.06E11 years
  • Sm-151 – 90 years
  • Sm-153 – 46.7 hours

Scandium

  • Sc-44 – 3.927 hours
  • Sc-46 – 83.83 days
  • Sc-47 – 3.351 days
  • Sc-48 – 43.7 hours

Selenium

  • Se-75 – 119.78 days
  • Se-79 – 65000 years

Silver

  • Ag-110 – 24.6 seconds
  • Ag-110m – 249.9 days
  • Ag-111 – 7.45 days

Sodium

  • Na-22 – 2.602 years
  • Na-24 – 15.00 hours

Strontium

  • Sr-85 – 64.84 days
  • Sr-87m – 2.81 hours
  • Sr-89 – 50.5 days
  • Sr-90 – 29.12 years
  • Sr-91 – 9.5 hours
  • Sr-92 – 2.71 hours

Sulfur

  • S-35 – 87.44 days

Technetium

  • Tc-101 – 14.2 minutes
  • Tc-99 – 2.13E5 years
  • Tc-99m – 6.02 hours

Tellurium

  • Te-125m – 58 days
  • Te-127 – 9.35 hours
  • Te-127m – 109 days
  • Te-129 – 69.6 minutes
  • Te-129m – 33.6 days
  • Te-131 – 25.0 minutes
  • Te-131m – 30 hours
  • Te-132 – 78.2 hours
  • Te-133 – 12.45 minutes
  • Te-133m – 55.4 minutes
  • Te-134 – 41.8 minutes

Terbium

  • Tb-160 – 72.3 days

Thallium

  • Tl-201 – 73.06 hours
  • Tl-207 – 4.77 minutes
  • Tl-208 – 3.07 minutes
  • Tl-209 – 2.20 minutes

Thorium

  • Th-227 – 18.718 days
  • Th-228 – 1.913 years
  • Th-229 – 7340 years
  • Th-230 – 7.7E4 years
  • Th-231 – 25.52 hours
  • Th-232 – 1.41E10 years
  • Th-234 – 24.10 days

Tin

  • Sn-119m – 293.1 days
  • Sn-123 – 129.2 days
  • Sn-125 – 9.64 days
  • Sn-126 – 1.0E5 years

Tungsten

  • W-181 – 121.2 days
  • W-185 – 75.1 days
  • W-187 – 23.9 hours

Uranium

  • U-232 – 72 years
  • U-233 – 1.59E5 years
  • U-234 – 2.445E5 years
  • U-235 – 7.03E8 years
  • U-236 – 2.34E7 years
  • U-237 – 6.75 days
  • U-238 – 4.47E9 years
  • U-240 – 14.1 hours

Vanadium

  • V-48 – 16.238 days

Xenon

  • Xe-131m – 11.9 days
  • Xe-133 – 5.245 days
  • Xe-133m – 2.188 days
  • Xe-135 – 9.09 hours
  • Xe-135m – 15.29 minutes
  • Xe-138 – 14.17 minutes

Ytterbium

  • Yb-169 – 32.01 days

Yttrium

  • Y-90 – 64.0 hours
  • Y-91 – 58.51 days
  • Y-91m – 49.71 minutes
  • Y-92 – 3.54 hours
  • Y-93 – 10.1 hours

Zinc

  • Zn-65 – 243.9 days
  • Zn-69 – 57 minutes

Zirconium

  • Zr-93 – 1.53E6 years
  • Zr-95 – 63.98 days
  • Zr-97 – 16.90 hours