 − 3 × 1018 years , giving about 1 alpha decay per two minutes in every kilogram of natural europium . This value is in reasonable agreement with theoretical predictions . Besides the natural radioisotope 151Eu , 35 artificial radioisotopes have been characterized , the most stable being 150Eu with a half @-@ life of 36 @.@ 9 years , 152Eu with a half @-@ life of 13 @.@ 516 years , and 154Eu with a half @-@ life of 8 @.@ 593 years . All the remaining radioactive isotopes have half @-@ lives shorter than 4 @.@ 7612 years , and the majority of these have half @-@ lives shorter than 12 @.@ 2 seconds . This element also has 8 meta states , with the most stable being 150mEu ( t1 / 2 = 12 @.@ 8 hours ) , 152m1Eu ( t1 / 2 = 9 @.@ 3116 hours ) and 152m2Eu ( t1 / 2 = 96 minutes ) . 
