HF

[Kavee Dodampahala 4E]

Why is HF not a strong acid even though fluorine is very electronegative?

[005391550]

because F is so electronegative, it pulls electrons harder and the bond between H and F is stronger and so HF doesn't lose protons (H+) as easily.

[Ying Yan 1F]

^Furthermore, because F is so electronegative, the H-F bond is shorter, and make it harder for the H+ ion (aka proton) to dissociate from the HF molecule.

[Fiona Latifi 1A]

HF also has a relatively large pKa value and a small Ka value, which makes it a weak acid.

[Juliet Stephenson 4E]

HF is a weak acid because the H-F bond is incredibly strong due to the electronegativity of F and the small atomic radius of F. As a result, it has short bonds that aren't equally broken, which translates to low levels of dissociation.