This table presents properties of nuclides, both stable and radioactive, adopted from the 7 th edition of the Table of Isotopes. i The data are based on experimental results reported in the literature, with the cutoff date varying from January to December, 1977. (The earliest date refers to the lightest nuclides, and vice versa.) Most mass excesses are from the 1977 Atomic Mass Evaluation,2 with some recent experimental values added. F'or a few of the very unstable nuclides for which no values were reported in the 1977 Atomic Mass Evaluation, estimates are taken from the tables of W.O. Myers. 3 Natural isotopic abundances 4 and neutron cross sections 5 are taken from compilations by N.E. Holden. F'or other references, original data, and information on the data measurements, the reader is referred to reference 1. Column 1, Nuclide: Nuclides are listed in order of increasing atomic number (Z), and are subordered by increasing mass number (A). All isotopic species with half-lives longer than about 1 s are included, as are the few shorter lived ground states, fission isomers, and "historic" isomers (e.g., 24mNa). Isotopes in reference 1 with ambiguous or very uncertain assignments, or whose assignments are probably in error (class "G"), have been omitted. Also not included are those nuclides identified in nuclear reactions, but for which radioactive decay has not been observed (class "R" in reference 1). Isomeric states aroe denoted by the conventional symbols m, m i , m 2 , etc. Identical mass assignments (with no "m") for several species indicate that the relative positions of the isomers are unknown. Column 2, t1/2 or abundance: Half-lives are given in plain type, natural isotopic abundances in italics. Half-lives are rounded so that the uncertainty is~5 units in the last place. A question mark following the half-life indicates that the assignment of the half-life (and other measured decay properties) to the listed values of Z and A is rather uncertain (nuclides with class "F''' in reference 1). Abundances are also rounded to an uncertainty of :$5 units in the last place, although the uncertainties are not well known. (Note that, because of the rounding, the abundances for an element do not always add to exactly 100%.) F'or additional information on abundances observed in specific sources and variations in abundances, the reader is referred to references 1 and 4. Column 3, Decay Mode: (3-rregative beta decay (3+ and/or EC positive beta decay. The entry of these modes alone or in various combinations involves the following conventions-f3+ ,EC or FC,p+: both (3+ 20.38 m (3' 99.76%, 10.650 3/2-EC 0.2 4 %,00 l' 98.89%
