If I were to compare the electronegativities of Al and Ga, shouldn't I be saying that the electronegativity of elements (in general) decreases down the group, I say this by thinking of the position of fluorine amongst the halides and about the metallic character trends (which increases down the group) so Al should be more electronegative. However Wikipedia's data page says otherwise. For aluminium it's 1.61 whereas for gallium it's 1.81 (I'm using the Pauling Scale). I then calculated $Z_{eff}$ values for both of them using Slater's rule which indicated a greater effective nuclear charge for gallium, so is this due to the poor shielding by d-orbitals?
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1$\begingroup$ The classical explanation is poor shielding by 3d orbitals, see also chemistry.stackexchange.com/a/49598/16683 $\endgroup$ – orthocresol♦ Apr 18 '17 at 13:16
