Mononuclidic elements
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Mononuclidic elements are chemical elements which either have only one stable isotope, or for which there is only one very long-lived isotope that dominates the element's natural isotopic abundance. There are nineteen elements in the first category, and three ( Bi, Th and Pa) in the second.[1] Elements such as Rb, In, and La, that have a single stable isotope and a significant fraction of a very long-lived isotope in their natural abundance, are not considered mononuclidic.
Use in metrology
Mononuclidic elements are of scientific importance because their atomic weights can be measured to high accuracy, since there is minimal uncertainty associated with the isotopic abundances present in a given sample.[1]
Contamination by unstable trace isotopes
Trace concentrations of unstable isotopes of some mononuclidic elements are found in natural samples. For example, 10Be, with a half-life of 1.5 million years, is produced by cosmic rays in the Earth's upper atmosphere; 129I, with a half-life of 15.7 million years, is produced by various cosmogenic and nuclear mechanisms; 137Cs, with a half-life of 30 years, is generated by nuclear fission. Such isotopes are used in a variety of analytical and forensic applications.
Complete list
Data from Atomic Weights and Isotopic Compositions ed. J. S. Coursey, D. J. Schwab and R. A. Dragoset, National Institute of Standards and Technology (2005).
| Nuclide | Z (p) | N (n) | isotopic mass (u) |
|---|---|---|---|
| 9Be | 4 | 5 | 9.012 182(3) |
| 19F | 9 | 10 | 18.998 403 2(5) |
| 23Na | 11 | 12 | 22.989 770(2) |
| 27Al | 13 | 14 | 26.981 538(2) |
| 31P | 15 | 16 | 30.973 761(2) |
| 45Sc | 21 | 24 | 44.955 910(8) |
| 55Mn | 25 | 30 | 54.938 049(9) |
| 59Co | 27 | 32 | 58.933 200(9) |
| 75As | 33 | 42 | 74.921 60(2) |
| 89Y | 39 | 50 | 88.905 85(2) |
| 93Nb | 41 | 52 | 92.906 38(2) |
| 103Rh | 45 | 58 | 102.905 50(2) |
| 127I | 53 | 74 | 126.904 47(3) |
| 133Cs | 55 | 78 | 132.905 45(2) |
| 141Pr | 59 | 82 | 140.907 65(2) |
| 159Tb | 65 | 94 | 158.925 34(2) |
| 165Ho | 67 | 98 | 164.930 32(2) |
| 169Tm | 69 | 100 | 168.934 21(2) |
| 197Au | 79 | 118 | 196.966 55(2) |
| 209Bi | 83 | 126 | 208.980 38(2) |
| 232Th | 90 | 142 | 232.0381(1) |
| 231Pa | 91 | 140 | 231.035 88(2) |
See also
References
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
