Question

beta decay of krypton-87

Answer 1

Beta radiation is made up of electrons ejected from an unstable nucleus (excessive neutrons); but the nuclei does not contain electrons. Therefore, the underlying reaction is the decomposition of a neutron.
When the neutron decomposes, it forms an electron, which is immediately ejected as a bete radiation, and a proton, which is captured by the nucleus. So, beta decay results in an increase in atomic number.

So the Beta decay of Krypton-87
\[_{36}^{87} Kr \rightarrow _{37}^{87} Rh + _{-1}^{0}e\]