Cell Biology Video Lessons. Genetics Video Lessons. Biochemistry Video Lessons. GOB Video Lessons. Microbiology Video Lessons. Calculus Video Lessons. Statistics Video Lessons. Microeconomics Video Lessons. Macroeconomics Video Lessons. Accounting Video Lessons. If my reasoning is incorrect, what is the actual reasoning that will support the correct acidity in both the cases?
You are right that electronegativity is an important consideration but another factor that is also very important is size of the atom. This allows the charge to be distributed over a larger volume of space, decreasing inter-electronic repulsions, providing greater stabilisation of the negative charge.
However, the greater size decreases charge density, decreasing the strength of ion-dipole interactions between the anion and the surrounding water molecules.
Thus, the extent of solvation decreases for the larger anion. Electronegativity is defined as the ability of the atom to attract a bonding pair of electrons. It merely serves as a proxy for the ability of the atom to stabilise negative charge. It should not be viewed as the most important factor that influences the atom's ability to stabilise negative charge. Also, mentioned in your answer, the strength of the bond formed with the larger atom with more diffuse orbitals decreases.
Consolidating the above discussion, there are really two factors on each side of the table below. Perhaps, the distribution of charge increases very significantly and the bond energy also decreases significantly while the decrease in extent of solvation and the electronegativity exhibit a relatively less significant effect. It would be great if someone is able to quantitatively show this It is not just electronegativity. You also have to look at how strongly the atom bonds to hydrogen.
If a strong bond forms, it might convince the atom to act as a base even if it would be grumpy based on its electronegativity. If only a weak bond forms, even an atom with relatively low electronegativity might balk at being protonated. It's due to favorable covalent overlap; take account of orbital sizes and nodes. Acidity is a bulk property - it depends on the medium where a substance acts as an acid.
Sulfurous acid. HSO 3 -. Hydrogen sulfite ion. SO 4 Sulfate ion. Phosphoric acid. Dihydrogen phosphate ion. Nitrous acid. HNO 2. Nitrite ion. Hydrofluoric acid. Fluoride ion. Methanoic acid. HCO 2 H. HCO 2 -. Methanoate ion. Benzoic acid. Benzoate ion. Oxalate ion.
Ethanoic acid. CH 3 COO. Ethanoate acetate ion.
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