What is the effect on electronegativity as you move from top to bottom in a group?

As you move from top to bottom in a group of the periodic table, electronegativity decreases. This trend occurs due to the increasing atomic radius as you add additional electron shells, which increases the distance between the nucleus and the valence electrons.

As the atomic number increases and additional electron shells are added, the effective nuclear charge experienced by the valence electrons does not increase proportionally due to electron shielding. This shielding effect reduces the attraction that the nucleus has on the valence electrons, making it less effective at attracting electrons from other atoms. Consequently, elements located lower in a group are less electronegative compared to those higher up in the group, as the greater distance from the nucleus diminishes its ability to attract bonding electrons.

This phenomenon is fundamental to understanding chemical bonding and reactivity, as electronegativity plays a crucial role in predicting how atoms will interact in chemical reactions.