A nucleus changes into a new element by emitting nuclear radiations; these changes are described using nuclear equations.
Beta decay changes the atomic number by plus one (the nucleus gains a proton) but the mass number remains unchanged (it gains a proton but loses a neutron by ejecting an electron, so a beta particle is an electron).
Gamma is pure energy and will not change the structure of the nucleus in any way.
Uranium 238, 23892U, emits an alpha particle to become what nucleus?
Alpha decay (two protons and two neutrons) changes the mass number of the element by minus four and the atomic number by minus two so the remaining nucleus will be 23490.
A periodic table shows that element number 90 is thorium,23490Th.
Positron emission changes the atomic number by minus one (the nucleus loses a proton) but the mass number remains unchanged. Neutron emission does not change the atomic number but the mass number reduces by one.