The shielding effect explains why valence-shell electrons are more easily removed from the atom . The effect also explains atomic size . The more shielding, the further the valence shell can spread out and the bigger atoms will be. The effective nuclear charge is the net positive charge experienced by valence electrons.

The nuclear force is exerted by the nucleus+ protons on the electrons in the outer shells. This is an attractive force, and kind of binds the electrons to the atoms. This reduces the potential of the electrons to interact with electrons in other atoms. Any interaction between 2 atoms is facilitated only by atoms. When this interaction is reduced, the stability of the atom increases.