In oxyacids of halogen, X=O bond is formed because of

Given, oxyacids of halogen, X=O bond is formed.

Formula/concept used: p-Block Elements

Detailed solution: In oxyacids the central atom is halogens is in ${\mathrm{sp}}^3$ hybridization. The half filled d orbital of halogen overlaps with the p-orbital of O to form $\mathrm{d}\pi -\mathrm{p}\pi \text{ overlapping }.$

So, the oxyacids of halogen formed X=O bond because of $\mathrm{d}\pi -\mathrm{p}\pi \text{ overlapping }.$