Oxygen atoms in acid structures?

[005199750]

If I start with an H–––O–––Cl molecule lewis acid structure, why would adding additional oxygens to the acid structure make it a stronger acid?

[lukezhang2C]

I'm guessing it's because this would make the molecule larger while also making it more electronegative, which makes it a stronger acid, but I'm not 100% sure.

[Chem_Mod]

This has to do with resonance. The more oxygens, the more double bonds. You can draw out the Lewis structures for yourself if necessary.
If there is more resonance, then the negative charge on the oxygen that results from losing a proton is better stabilized. Since the conjugate base is more stable, that means it's a strong acid.

[mayra martinez 1D]

Oxygens tend to form more double bonds, both with each other and with other elements and so that makes the molecule more negative and strong.