# The elements with the highest electronegativity values tend to be found where on the periodic table?

Jul 23, 2016

Electronegativity increases ACROSS a Period, and decreases down a Group.

#### Explanation:

Electronegativity is defined as the tendency of an atom in a chemical bond to polarize electron density towards itself. Two factors are important here: (i) nuclear charge; and (ii) shielding by other electrons.

As we face the table, nuclear charge increases sequentially from left to right as $Z$ increases.

Electronegativity should be greater for the rightmost elements (as we face the Table). And in fact fluorine and oxygen are the MOST electronegative elements. (Noble Gases do not tend to form chemical bonds and so escape consideration).

Down a Group, the nuclear charge tends to be shielded by inner core electrons, and thus fluorine is more electronegative than chlorine, which is more electronegative than bromine etc. Incomplete electron shells tend to shield each other very imperfectly, and this is manifested by the well known decrease in atomic radius across the Period from left to right.

So the important point to note: $\text{Electronegativity increases across a Period}$.