The nuclide ^238_92U finally changes to the stable ^206_82Pb through a series of alpha and beta^- emissions. The numbers of alpha and beta^- particles emitted are respectively

JEE Main levelSingle correct optionDifficulty 2 of 3as173

The nuclide $X_{92}^{238} X_{292}^{2238} U$ finally changes to the stable $X_{82}^{206} X_{282}^{2206} Pb$ through a series of $α$ and $β^{-}$ emissions. The numbers of $α$ and $β^{-}$ particles emitted are respectively

Mass number drops by

238 - 206 = 32

, so number of

α

32/4 = 8

. These 8

α

emissions lower

Z

by 16, but

Z

falls only by

92 - 82 = 10

, so

16 - 10 = 6

β^{-}

particles must be emitted.