Question

How does electronegativity for the halogens?

Answer 1

Looking at the Table, electronegativity increases across the Period from left to right.........

Explanation:

...........but decreases down the Group. Electronegativity is defined as the ability of atom involved in a chemical bond to polarize electron density towards itself. In the same valence shell, i.e. in the same Period it makes sense that nuclear charge should increase incrementally across the Period, with the most electronegative element the first Group VII member, fluorine.

Going DOWN the Group, however, while nuclear charge has increased, there is a full electronic shell between the nucleus and the valence electrons, with increased shielding effects, and it follows that nucleus/valence electron attraction should decrease. And thus electronegativitiy values decrease down a Group, a vertical column, on the Periodic Table.

And thus in terms of electronegatvity: `F>Cl>Br>I>At`. To quote figures, and of course as physical scientists we should do so, `F` has a Pauling electronegativity of `4.0` decreasing sequentially to `At, 2.2`.