What is the trend in electronegativity with increasing atomic number?

1 Answer
anor277
Sep 17, 2015

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.

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