Carbon (Z = 6) with mass number 11 decays to boron (Z = 5). (a) Is it a β+ -decay or a β− -decay? (b) The half-life of the decay scheme is 20.3 minutes. How much time will elapse before a mixture of 90 % carbon - 11 and 10% boron - 11 (by the number of atoms ) converts itself into a mixture of 10% carbon - 11 and 90 % boron - 11 ?
Hence it is aβ−decay
(b)Let the total no. of atoms be100 N1
Initially 90 N 10N0
Fimlly 10N0 90 N0
Now,10N0=90 N0 e−λt