Strength of an acid

[Simrina Desar Dis 1H]

How does electronegativity affect the relative strength of an acid?

[Sabah Islam 1G]

Electronegativity affects the relative strength of an acid because the more electronegative an atom is, the more likely it wants to "hold on" to the hydrogen atom attached to it, therefore making it harder for the acid to deprotonate and for the H+ ion to detach from it. For example, comparing HF and HCl, fluoride is more electronegative, so it is stronger in holding to the hydrogen atom, but chloride is less electronegative, so it would be easier to pull the H+ ion away for it than it would be from the fluoride.

[804899546]

Then how come HF is a stronger base than HOH, even though fluorine is more electronegative than oxygen? Does the strength of an acid increase as we go across the periodic table?

[Michelle Steinberg2J]

So acids with longer bonds are stronger than ones with shorter bonds? For example, HCl has a longer bond than HF, but is stronger?

[fara valdez]

I think it relies on which bond is the most electronegative.

[fara valdez]

Im also interested in that question: is it standard that acids with longer bonds are stronger?

[EllenRenskoff-1C]

For an oxoacid, the rules would be slightly different as it is dependent on if the resulting anion is stabilized by delocalizing the negative charge. Basically, if the compound is Cl-O-H, it will be more acidic than I-O-H because it is more stabilized.The Cl is more electronegative than I, so it pulls more electrons away from the O than does the I. This would stabilize the charge more in the respective compound. So in this case, the rule regarding longer bonds being stronger acids does not necessarily apply because in the presence of oxygen, the strength of the acid is more dependent on the stability of the negative charge than the bond length.

[RubyLake1F]

Why is it a rule that the more electronegative an atom is that is attached to hydrogen, the stronger the acid (in reference to molecules like HCl vs. H2S)? This seems counterintuitive, because a higher electronegativity difference should mean a more ionic and therefore a stronger bond.

[204917020]

Strong acids and bases completely dissociate in solution. Therefore, they must have a small change in electronegativity between atoms in order for the molecule to completely dissociate in solution. On the other hand, weak acids and bases may partially dissociate in solution, but they do not completely dissociate.

[Shione Nakahara 1F]

As you go down the group of the periodic table, acidity increases with the decrease of electronegativity (since the size of the atom increases). The smaller the atom, the shorter the bond and thus harder for them to dissociate in water. In my notes from class it says that HF<HCl<HBr<HI which goes from less acidic (short, strong bond) to more acidic (long, weaker bond).

[Yixiao Hu 3C]

higher electronegativity difference means stronger acids (imagine H2S and HF)

[105002507]

The higher the electronegativity difference, the stronger the acid

[Hilda Sauceda 3C]

Across a row in periodic table, acidity increases with the increase in electronegativity.

[Jocelyne Milke 1G]

The more electronegative an atom, the more willing it is to hold onto the electrons left over when the Hydrogen leaves the molecule.

[ChemSection3I]

I was also wondering this, thanks for clarifying!