Answer is: α decay, β- decay, β- decay.
1) Nuclear reaction 1: ²³⁸U → ²³⁴Th + α (alpha particle).
Alpha particle is nucleus
of a helium-4 atom, which is
made of two protons and
two neutrons.
Alpha decay is radioactive decay in
which an atomic nucleus emits
an alpha particle (helium
nucleus) and transforms into an atom with an atomic
number that is reduced by two and mass number that is reduced by four.
2) Nuclear reaction 2: ²³⁴Th → ²³⁴Pa + e⁻ + electron neutrino.
In beta
minus decay, neutron is converted to a proton and
an electron and an electron antineutrino and atomic
number Z is increased by one.
3) Nuclear reaction 3: ²³⁴Pa → ²³⁴U + e⁻ + electron neutrino
