Answer is an alpha emission
Alpha decay is an emission of ₂⁴He nucleus. If an
element undergoes an alpha decay, the mass of the daughter nucleus formed is reduced
by 4 compared
to mass of parent atom and atomic number is reduced by 2 compared to atomic number of parent
atom.
Here parent atom is Sm which has
atomic number as 62 and mass number as 146. Since the emitted particle is a ₂⁴He nucleus this is an alpha decay. Daughter atom will
have 146 - 4 = 142 as mass number and 62 - 2 = 60 as atomic number. Hence, daughter atom should
be Nd which has atomic number as 60.
