How does an atom with too few neutrons relative to protons undergo radioactive decay? *

by converting proton to a neutron

by converting a neutron to a proton

by emitting an alpha particle

An atom with too few neutrons relative to protons (or neutron-poor atom) undergoes radioactive decay by converting the proton to a neutron. There are two ways to convert the proton to a neutron, and the way depends on the atomic number of the atom.

If the atom has the atomic number smaller than 83 it will decay by capturing an electron, while the atom with an atomic number greater than 83 will decay by positron emission.