سيريوم المعرفة
Naturallyoccurring cerium is composed of 4 stable isotopes; 136 Ce, 138 Ce, 140 Ce, and 142 Ce with 140 Ce being the most abundant (% natural abundance). 136 Ce and 142 Ce are predicted to be double beta active but no signs of activity were ever observed (for 142 Ce, the lower limit on halflife is 5×10 16 years). 26 radioisotopes have been characterized with the most longlived being ...