Electronegativity

[melissa_dis4K]

Between atoms like chloride and oxygen how do you determine which has a higher electronegativity given that electronegativity increases as you go up and across to the right?

[Tarika Gujral 1K]

Electronegativity follows a diagonal trend: increasing towards the upper right: however, period is more important than group. This is because a lower period is associated with fewer energy shells, and thus a higher Zeff. Higher Zeff implies greater electronegativity: because the stronger the nuclear pull, the greater the pull on electrons.

[Joaquin Andrade]

Because Cl is a period beneath O, it is affected by shielding, which reduces the pull of the nucleus on valence electrons. Thus, O will be more electronegative even though Cl is a group to the right.