اذا لم تجد ما تبحث عنه يمكنك استخدام كلمات أكثر دقة.
العُنْصُر الرَّابَع والتِسْعُون:- a solid silvery gray radioactive transuranic element whose atoms can be split when bombarded with neutrons; found in minute quantities in uranium ores but is usually synthesized in nuclear reactors; 13 isotopes are known with the most important being plutonium 239 (Arabic WordNet)