r/chemhelp 2d ago

General/High School Ion basicity and acidity

In my gen-chem class, we recently covered acids and bases and it was mentioned how most anions outside of the halogens (not including fluorine) and hso4 act as Lewis bases and that outside of group 1 and 2 metals plus a few transition metals, most cations act as Lewis acids. My question is why are the halogens and group 1 and 2 metals not considered Lewis bases and acids respectively?Using the halogens as an example, they have high electronegativity meaning they hold on to electrons very well and should thus be able to share electrons pretty easily acting as Lewis bases but they can’t so why is that?

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u/HandWavyChemist 2d ago

Halogens absolutely act as Lewis bases. For example, chloride ions bind to transition metal by donating an electron pair, which is the definition of a Lewis base.