Coulomb's Law says that the force of attraction or repulsion between 2 charged particles is proportional to the charges and the distance between them: F?Q1Q2/d^2. An electron in an atom of Lithium sees an effective nuclear charge of 1.91 at a radius of 152pm. An electron in an oxygen atom sees an effective nuclear charge of 4.45 at a radius of 73pm. How much greater is the attraction between an oxygen electron and the nucleus as compared to an electron in the lithium atom. How does this relate to the first ionization energy of the two atoms? Are there any other contributing factors that affect the ionization energies? How do these numbers relate to the positions of the 2 elements on the periodic table?