Answer:
(a) 217 Ra (b) 29 P
84 16
Explanation
(a) 221 Rn ---------------> 4 He + 217 Ra
86 2 84
the mass number is reduced by 4 while the atomic number is reduced by 2 since an alpha particle is emitted
(b) 29 P ------------------> 0 e + 29 P
15 -1 16
the mass number remains the same while the atomic number is reduced by -1 since a beta particle is emitted
