What makes an atom stable? When is its nucleus stable and when does it have electronic stability?

Here, we have to look at two different stabilities of
atoms. One is the radioactive stability that involves forces between the particles that
make up the nucleus and the other is the chemical stability that involves the electronic
configuration of atoms.

The nucleus of atoms consists of
protons and neutrons. There is a strong force of repulsion between the protons as they
have the same electric charge. These forces are balanced by a strong nuclear force that
ensures the nucleus of atoms does not break apart.

For
atoms which have more than 83 protons in their nucleus the strong nuclear force is less
than the force of repulsion between the protons; this makes them unstable and they
undergo radioactive decay processes and convert to forms with a stable
nucleus.

Chemical stability is reached when atoms have the
electronic configuration of the closest noble gas. This can be achieved by either
sharing electrons as in covalent bonds or giving up or accepting electrons as in ionic
bonds.

Chemical stability is reached by the rearrangement
of electrons and nuclear stability is reached by a change in the constituents of the
nucleus of atoms.