Relative Acidity

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Relative Acidity

Postby Meghanhe1l » Thu Dec 06, 2018 7:32 pm

The textbook states that with greater electronegativity on the central atom, the higher the acidity of the compound. Yet it also states that the greater the atomic size of the central atom, the greater the acidity. Because electronegativity goes up going up a group, and radius goes up going down a group, don't these two rules contradict one another?

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Re: Relative Acidity

Postby Tiffany_Cacy_3D » Thu Dec 06, 2018 8:08 pm

Those rules are only applicable in certain situations. When you have the case where you're looking at two acids that they all have the same configurations such as ClOH, BrOH, and IOH you can't look at the atomic radius because the hydrogens are not directly attached to the differing atoms. In this case you would look at the electronegativity of the different atoms, Cl,Br, and I. When considering electronegativity we know that the higher electronegativity the atom has the more it will stabilize the left over O- and the since Cl has the highest electronegativity it has the most stable conjugate base making it a stronger acid then those with lower electronegativities. If the hydrogens are attached directly to the same atoms in question, HCL, HBr, HI then you can just look at atomic radius because that will determine how strong those bonds are and which one is most likely to lose their H ions more easily.

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