Alpha particle is nucleus
of a helium-4 atom, which is
made of two protons and
two neutrons.
Nuclear reaction: ₈₄²¹⁸Po → ₈₂²¹⁴Pb + α (alpha particle).
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.
