Answer
See explanation.
Work Step by Step
a. The alpha particle has a charge of +2 and a mass number of 4, so the new nucleus will have a mass number of 239 – 4 = 235, and an atomic number of 94 – 2 = 92. It is uranium, $^{235}_{92}U$.
b. The $\beta^-$ particle has a charge of -1 and a mass number of 0, so the new nucleus will have a mass number of 24, and an atomic number of 11 – (-1) = 12. It is magnesium, $^{24}_{12}Mg$.
c. The $\beta^+$ particle has a charge of +1 and a mass number of 0, so the new nucleus will have a mass number of 15, and an atomic number of 8 – (1) = 7. It is nitrogen, $^{15}_{7}N$.
