Who developed the study of radioactivity?

The reaction $_5B^8 \to _4Be^8 + _1e^0$ is due to

If it is assumed that ${}_{92}^{235}U$ decays only by emitting $\alpha$ and $\beta$ particles, the possible product of the decay is:

Which is not emitted by a radioactive substance?

If uranium (mass number $238$ and atomic number $92$) emits an $\alpha$-particle,what are the mass number and atomic number of the product?

If a radioactive isotope with atomic number $A$ and mass number $M$ emits an $\alpha$-particle,the atomic number and mass number of that new isotope will become: