The electronegativity, or the tendency of an atom to attract electrons to it in a bond, increases moving from left to right across one row. The extra shells of electrons present in elements found in the lower part of the periodic table act as a shield between the outer electrons of a large atom and the nucleus. The attraction between the outer electrons and the nucleus is therefore less and the electronegativity decreases. An exception to this trend are the noble gases in group 8A. Since most of these elements have not been shown to form bonds, most do not have electronegativity values associated with them.
