Question

What is the trend in electronegativity with increasing atomic number?

Answer 1

For a given period, electronegativity should increase with atomic number.

Explanation:

Electronegativity is conceived to be the ability of an atom bound to another atom to polarize electron density towards itself. Two issues affect this ability: nuclear charge; and size of the nucleus.

Electrons in incomplete shells shield nuclear charge very ineffectively. Towards the RHS of the periodic table are the most electronegative elements, i.e. `O`, and `F`; where their valence electrons experience the increased nuclear charge. Once a period is descended, however, the inner shell electrons shield the increased nuclear charge. This is why (on the Pauling scale), `F`, has an assigned electronegativity value of `4`, and `O`, `3.5`. whereas is if we go down a period to `Cl`, the electonegativity of `Cl` = `3.1` So electronegativity should increase across a period, but decreases down a group.