Question

Why does electronegativity increases across a period?

Answer 1

As we go across a period we increase nuclear charge. What should be the result for electron-nucleus attraction?

Explanation:

Electronegativity is conceived to be the ability of an atom in a chemical bond to polarize electron density towards itself. Nuclear charge clearly is the predominant influence, and in fact the halogens on the RHS of the periodic table should be the most electronegative elements; and indeed they are.

So electronegativity increased across a period but decreases down a Group. Why?