Question

A radioactive nucleus undergoes a series of decay according to the scheme
`A overset(alpha)rarr A_(1) overset(beta^(-))rarr A_(2) overset(alpha)rarr A_(3)^(172) overset(gamma)rarr A_4`.

Answer 1

Emission of 2 alpha particles decreases the mass number by 8 and charge number 4. Emission of one `beta` particle increase the charge number by 1 without affecting mass number. `gamma` emission affects neither of two. Therefore, for `A_4`: mass no. =`180-8=172` charge no. =`72-4+1=69`