Isotopes of berkelium

Berkelium (₉₇Bk) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was ²⁴³Bk in 1949. There are 20 known radioisotopes, from ²³⁰Bk and ²³³Bk to ²⁵³Bk (with the exception of ²³⁵Bk and ²³⁷Bk), and 6 nuclear isomers. The longest-lived isotope is ²⁴⁷Bk with a half-life of 1,380 years.