- Element effects: The acidity of H – A increases both left-to-right across a row and down a column of the periodic table.
- Inductive effects: The acidity of H– A increases with the presence of electron-withdrawing groups in A.
- Resonance effects: The acidity of H– A increases when the conjugate base A:– is resonance stabilized.
- Hybridization effects: The acidity of H – A increases as the percent s-character of A:– increases.