Factors That Affect Acid Strength

Series of oxoacids… O atoms bonded to Y…
For a series of oxoacids, (HO)mYOnv, the acid strength increases with n, the number of O atoms bonded to Y (excluding O atoms in OH group)
Oxoacids and Electronegativity…

For a series of oxoacids of the same structure, differing only in the atom, Y, the acid strength increases with the electronegitivity of Y


(Direct Relationship)


The acid strength of a polyprotic acid and its anions decrease with increasing negative charge


(Inverse Relationship)

Across periodic table…

Going across a row of elements of the periodic table, the electronegativity increase, the H-X bond polarity increases; which means there is a higher partial positive/negative – weaker bond; thus, the acid strength increases


(Direct Relationship) 

Going down a column…
Going down a column of elements of the periodic table, the size of an atom X increases, the H-X bond strength decreases, and the strength of the binary acid increase.

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