Explain why fluorine forms only one oxoacid, HOF.

Explanation

Chlorine, bromine and iodine form four series of oxacids of the general formula HOX, HOXO, `HOXO_(2) and HOXO_(3)` in which the oxidation states of halogen (X = Cl, Br or I) is +1, +3, +5 and +7 respectively. But fluorine forms only one oxoacid, HOF that too at low temperature in which the oxidation state of F is +1.
`overset(0)(F_(2))+H_(2)O(ice) overset(233 K)hArr overset(+1)(HOF) + overset(-1)(HF)`
However, due to the absence of d-orbitals, F cannot show higher positive oxidation states, of +3, +5 and +7 and hence F does not form higher oxoacids such as HOFO, `HOFO_(2) and HOFO_(3)` is which the oxidation states of F are +3, +4 and +7 respectively.