What happens to the mass number and atomic number of an element when it emits $\gamma$-radiation?

Assertion: ${}^{90}Sr$ from the radioactive fallout of a nuclear bomb ends up in the bones of human beings through the milk consumed by them. It causes impairment of the production of red blood cells.
Reason: The energetic $\beta$-particles emitted in the decay of ${}^{90}Sr$ damage the bone marrow.

During negative $\beta$-decay,which of the following processes occurs?

In the nuclear reaction,${ }_6^{11} C \rightarrow{ }_5^{11} B + \beta^+ + X$,$X$ stands for

$U^{238}$ decays into $Th^{234}$ by the emission of an $\alpha$-particle. There follows a chain of further radioactive decays,either by $\alpha$-decay or by $\beta$-decay. Eventually,a stable nuclide is reached,and after that,no further radioactive decay is possible. Which of the following stable nuclides is the end product of the $U^{238}$ radioactive decay chain?

$A$ radioactive source is placed in a uniform electric field. If $\alpha, \beta$,and $\gamma$ particles are emitted,then $\alpha, \beta, \gamma$ particles correspond to which paths respectively?