Why would an atomic nucleus give off a particle? question 2 options: to become stable to increase atomic mass to change atomic number to emit radiation

An atomic nucleus would give off a particle to become stable. 
An atom is unstable if the forces among the particles that make up the nucleus are unbalanced; if the nucleus has an excess of internal energy. Instability of an atom's nucleus may result from an excess of either neutrons or protons. An unstable nucleus would attempt to attain stability by giving off the nucleons (protons or neutrons), as well as other particles or by releasing energy in other forms.