When Is Atom Stable?

An atom is stable if the forces among the particles that makeup the nucleus are balanced. An atom is unstable (radioactive) if these forces 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.

How do you know if an atom is stable?

When the atom is stable, it has a net electrical charge of 0, meaning that the number of protons equals the number of electrons. The nucleus is also balanced, in that the number of protons equals the number of neutrons.

When an atom is the most stable?

Atoms are at their most stable when their outermost energy level is either empty of electrons or filled with electrons. Sodium atoms have 11 electrons. Two of these are in the lowest energy level, eight are in the second energy level and then one electron is in the third energy level.