radioactive isotope

radioactive isotope

radioactive isotope or radioisotope, natural or artificially created isotope of a chemical element having an unstable nucleus that decays, emitting alpha, beta, or gamma rays until stability is reached. The stable end product is a nonradioactive isotope of another element, i.e., radium-226 decays finally to lead-206. Very careful measurements show that many materials contain traces of radioactive isotopes. For a time it was thought that these materials were all members of the actinide series; however, exacting radiochemical research has demonstrated that certain of the light elements also have naturally occurring isotopes that are radioactive. Since minute traces of radioactive isotopes can be sensitively detected by means of the Geiger counter and other methods, they have various uses in medical therapy, diagnosis, and research. In therapy, they are used to kill or inhibit specific malfunctioning cells. Radioactive phosphorus is used to treat abnormal cell proliferation, e.g., polycythemia (increase in red cells) and leukemia (increase in white cells). Radioactive iodine can be used in the diagnosis of thyroid function and in the treatment of hyperthyroidism. Since the iodine taken into the body concentrates in the thyroid gland, the radioaction can be confined to that organ. In research, radioactive isotopes as tracer agents make it possible to follow the action and reaction of organic and inorganic substances within the body, many of which could not be studied by any other means. They also help to ascertain the effects of radiation on the human organism (see radiation sickness). In industry, radioactive isotopes are used for a number of purposes, including measuring the thickness of metal or plastic sheets by the amount of radiation they can stop, testing for corrosion or wear, and monitoring various processes.

Stable isotopes are chemical isotopes that are not radioactive (to current knowledge). Stable isotopes of the same element have the same chemical characteristics and therefore behave almost identically. The mass differences, due to a difference in the number of neutrons, result in partial separation of the light isotopes from the heavy isotopes during chemical reactions (isotope fractionation). For example, the difference in mass between the two stable isotopes of hydrogen, 1H (1 proton, no neutron, also known as protium) and 2H (1 proton, 1 neutron, also known as deuterium) is almost 100%. Therefore, a significant fractionation will occur.

Commonly analysed stable isotopes include oxygen, carbon, nitrogen, hydrogen and sulfur. These isotope systems have been under investigation for many years in order to study processes of isotope fractionation in natural systems because they are relatively simple to measure. Recent advances in mass spectrometry (ie. multiple-collector inductively coupled plasma mass spectrometry) now enable the measurement of heavier stable isotopes, such as iron, copper, zinc, molybdenum, etc.

Stable isotopes have been used in botanical and plant biological investigations for many years, and more and more ecological and biological studies are finding stable isotopes (mostly carbon, nitrogen and oxygen) to be extremely useful. Other workers have used oxygen isotopes to reconstruct historical atmospheric temperatures, making them important tools for climate research.

Most of naturally occurring isotopes are stable; however, a few tens of them are radioactive with very long half-lives. If the half life of a nuclide is comparable to or greater than the Earth's age (4.5 billion years), a significant amount will have survived since the formation of the Solar System, and will contribute to the natural isotopic composition of a chemical element. The lowest half lives of such isotopes are around 700 million years (e.g., 235U). Many isotopes that are presumed to be stable (i.e. no radioactivity has been observed for them) are predicted to be radioactive with extremely long half-lives (sometimes as high as 1018 years or more). If the predicted half life falls into an experimentally accessible range, such isotopes have a chance to move from the list of stable nuclides to the radioactive category, once their activity is observed. Good examples are bismuth-209 and tungsten-180 which have been recently (2003) found to be alpha-active.

Most stable isotopes in the earth are believed to have been formed in processes of nucleosynthesis, in generations of stars that preceded the formation of the solar system. However, some stable isotopes show abundance variations in the earth as a result of decay from long-lived radioactive nuclides. These decay-products are termed radiogenic isotopes, in order to distinguish them from the much larger group of 'non-radiogenic' isotopes. They play an important role in radiometric dating and isotope geochemistry.

Research areas

The Island of Stability may reveal a number of stable atoms that are heavier (and with more protons) than lead.

Stable isotope fractionation

There are three types of isotope fractionation:

List of stable isotopes

There are 80 known elements which have at least one stable isotope. As of September 2007, there were 250 known stable isotopes. Tin has 10 stable isotopes, more than any other element. Xenon is the only element which has 9 stable isotopes. There is no element with exactly 8 stable isotopes. Only five elements have 7 stable isotopes. Mononuclidic elements are those that have a single isotope (stable or very long-lived) in their natural abundance; there are 27 of these. Every element from hydrogen to lead has at least one stable isotope with the exceptions of technetium and promethium; elements with more than 82 protons only have radioactive isotopes, although they can still occur naturally because their half-lives are of an order of magnitude not much less than that of the time since the death of a nearby star, or because they occur in a decay chain of another radioactive isotope with such a half-life. It wasn't until 2003 that bismuth-209 was shown to be radioactive. All stable isotopes are the ground states of nuclei, excluding tantalum-180m, which is the excited level (the ground state of this nucleus is radioactive), but its decay is extremely strongly forbidden by spin-parity selection rules.

  1. Hydrogen-1
  2. Hydrogen-2
  3. Helium-3
  4. Helium-4
  5. Lithium-6
  6. Lithium-7
  7. Beryllium-9
  8. Boron-10
  9. Boron-11
  10. Carbon-12
  11. Carbon-13
  12. Nitrogen-14
  13. Nitrogen-15
  14. Oxygen-16
  15. Oxygen-17
  16. Oxygen-18
  17. Fluorine-19
  18. Neon-20
  19. Neon-21
  20. Neon-22
  21. Sodium-23
  22. Magnesium-24
  23. Magnesium-25
  24. Magnesium-26
  25. Aluminium-27
  26. Silicon-28
  27. Silicon-29
  28. Silicon-30
  29. Phosphorus-31
  30. Sulfur-32
  31. Sulfur-33
  32. Sulfur-34
  33. Sulfur-36
  34. Chlorine-35
  35. Chlorine-37
  36. Argon-36
  37. Argon-38
  38. Argon-40
  39. Potassium-39
  40. Potassium-41
  41. Calcium-40
  42. Calcium-42
  43. Calcium-43
  44. Calcium-44
  45. Scandium-45
  46. Titanium-46
  47. Titanium-47
  48. Titanium-48
  49. Titanium-49
  50. Titanium-50
  51. Vanadium-51
  52. Chromium-50
  53. Chromium-52
  54. Chromium-53
  55. Chromium-54
  56. Manganese-55
  57. Iron-54
  58. Iron-56
  59. Iron-57
  60. Iron-58
  61. Cobalt-59
  62. Nickel-58
  63. Nickel-60
  64. Nickel-61
  65. Nickel-62
  66. Nickel-64
  67. Copper-63
  68. Copper-65
  69. Zinc-64
  70. Zinc-66
  71. Zinc-67
  72. Zinc-68
  73. Zinc-70
  74. Gallium-69
  75. Gallium-71
  76. Germanium-70
  77. Germanium-72
  78. Germanium-73
  79. Germanium-74
  80. Arsenic-75
  81. Selenium-74
  82. Selenium-76
  83. Selenium-77
  84. Selenium-78
  85. Selenium-80
  86. Bromine-79
  87. Bromine-81
  88. Krypton-78
  89. Krypton-80
  90. Krypton-82
  91. Krypton-83
  92. Krypton-84
  93. Krypton-86
  94. Rubidium-85
  95. Strontium-84
  96. Strontium-86
  97. Strontium-87
  98. Strontium-88
  99. Yttrium-89
  100. Zirconium-90
  101. Zirconium-91
  102. Zirconium-92
  103. Zirconium-94
  104. Niobium-93
  105. Molybdenum-92
  106. Molybdenum-94
  107. Molybdenum-95
  108. Molybdenum-96
  109. Molybdenum-97
  110. Molybdenum-98
  111. : Technetium - No stable isotopes
  112. Ruthenium-96
  113. Ruthenium-98
  114. Ruthenium-99
  115. Ruthenium-100
  116. Ruthenium-101
  117. Ruthenium-102
  118. Ruthenium-104
  119. Rhodium-103
  120. Palladium-102
  121. Palladium-104
  122. Palladium-105
  123. Palladium-106
  124. Palladium-108
  125. Palladium-110
  126. Silver-107
  127. Silver-109
  128. Cadmium-106
  129. Cadmium-108
  130. Cadmium-110
  131. Cadmium-111
  132. Cadmium-112
  133. Cadmium-114
  134. Indium-113
  135. Tin-112
  136. Tin-114
  137. Tin-115
  138. Tin-116
  139. Tin-117
  140. Tin-118
  141. Tin-119
  142. Tin-120
  143. Tin-122
  144. Tin-124
  145. Antimony-121
  146. Antimony-123
  147. Tellurium-122
  148. Tellurium-123
  149. Tellurium-124
  150. Tellurium-126
  151. Iodine-127
  152. Xenon-124
  153. Xenon-126
  154. Xenon-128
  155. Xenon-129
  156. Xenon-130
  157. Xenon-131
  158. Xenon-132
  159. Xenon-134
  160. Xenon-136
  161. Caesium-133
  162. Barium-132
  163. Barium-134
  164. Barium-135
  165. Barium-136
  166. Barium-137
  167. Barium-138
  168. Lanthanum-139
  169. Cerium-136
  170. Cerium-138
  171. Cerium-140
  172. Cerium-142
  173. Praseodymium-141
  174. Neodymium-142
  175. Neodymium-143
  176. Neodymium-145
  177. Neodymium-146
  178. Neodymium-148
  179. : Promethium - No stable isotopes
  180. Samarium-144
  181. Samarium-150
  182. Samarium-152
  183. Samarium-154
  184. Europium-153
  185. Gadolinium-154
  186. Gadolinium-155
  187. Gadolinium-156
  188. Gadolinium-157
  189. Gadolinium-158
  190. Gadolinium-160
  191. Terbium-159
  192. Dysprosium-156
  193. Dysprosium-158
  194. Dysprosium-160
  195. Dysprosium-161
  196. Dysprosium-162
  197. Dysprosium-163
  198. Dysprosium-164
  199. Holmium-165
  200. Erbium-162
  201. Erbium-164
  202. Erbium-166
  203. Erbium-167
  204. Erbium-168
  205. Erbium-170
  206. Thulium-169
  207. Ytterbium-168
  208. Ytterbium-170
  209. Ytterbium-171
  210. Ytterbium-172
  211. Ytterbium-173
  212. Ytterbium-174
  213. Ytterbium-176
  214. Lutetium-175
  215. Hafnium-176
  216. Hafnium-177
  217. Hafnium-178
  218. Hafnium-179
  219. Hafnium-180
  220. Tantalum-180m
  221. Tantalum-181
  222. Tungsten-182
  223. Tungsten-183
  224. Tungsten-184
  225. Tungsten-186
  226. Rhenium-185
  227. Osmium-187
  228. Osmium-188
  229. Osmium-189
  230. Osmium-190
  231. Osmium-192
  232. Iridium-191
  233. Iridium-193
  234. Platinum-192
  235. Platinum-194
  236. Platinum-195
  237. Platinum-196
  238. Platinum-198
  239. Gold-197
  240. Mercury-196
  241. Mercury-198
  242. Mercury-199
  243. Mercury-200
  244. Mercury-201
  245. Mercury-202
  246. Mercury-204
  247. Thallium-203
  248. Thallium-205
  249. Lead-206
  250. Lead-207
  251. Lead-208

See also

References

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