a) Alpha decay occurs when an unstable nuclide emits an alpha particle, (which is just a helium-4 atom), which contains 2 protons and 4 neutrons. This means that transmutation has occurred (since a nuclide of a different element will be produced), and this newly produced nuclide will have 2 fewer protons and 4 fewer neutrons than the original nuclide.
b) [tex]^{234}_{92} \text{U} \longrightarrow ^{4}_{2} \text{He}+^{230}_{90} \text{Th}[/tex]
c) Alpha decay occurs when an unstable nuclide emits a beta particle, (also known as an electron). This causes transmutation (since a nuclide of a different element will be produced), and this newly produced nuclide will have 1 more proton than the original nuclide.
d) [tex]^{131}_{53} \text{I} \longrightarrow ^{0}_{-1} \beta+^{131}_{54} \text{Xe}[/tex]
