140Ce

140Ce is a stable isotope of the element cerium (chemical symbol Ce) with atomic number 58 and mass number 140. It contains 58 protons and 82 neutrons. As a stable isotope, 140Ce does not undergo radioactive decay and has no measurable half-life.

In nature, cerium is represented by several isotopes, with 140Ce being the most abundant. The approximate natural abundances are about 0.19% for 136Ce, 0.25% for 138Ce, 88.5% for 140Ce, and 11.0% for 142Ce. This distribution makes 140Ce by far the dominant cerium isotope in terrestrial sources such as minerals and ores.

The nucleus of 140Ce is even-even, so its ground-state spin is 0 and its parity is positive. The neutron number 82 is a magic number, which contributes to the relative stability of this isotope within the cerium region of the periodic table.

140Ce occurs in minerals containing cerium, such as rare-earth ores and oxides like cerium oxide (CeO2). Because it is stable, it serves as a common reference and standard in isotopic analyses and in geochemical and cosmochemical studies that examine isotopic compositions and fractionation of cerium.

Overall, 140Ce is the most abundant, stable cerium isotope and an important reference point for understanding the isotopic composition of cerium in natural materials.