Question 54 of 72
Q.The radioactive lanthanide among the following is :
(a) promethium
(b) lutetium
(c) cerium
(d) gadolinium
Tamil Nadu DgeTamil Nadu HSC (DGE) Board 2018MCQ· 1mImportance★★★★★
75% · 54/72 Questions
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Start your 14-day free trial to unlock the full solution →Among the lanthanides, promethium is unique in having no stable, naturally occurring isotope — all of its isotopes are radioactive.
The lanthanide series (Ce to Lu, atomic numbers 58–71) consists mostly of elements with stable isotopes. Promethium (Z = 61) is the exception: it has no stable isotope at all (its longest-lived isotope, , has a half-life of only about 17.7 years). It occurs in nature only in trace amounts from the spontaneous fission of uranium, and is other …
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