Chemistry - GOC Question with Solution | TestHub

Down the group the halide ion gets larger, so the negative charge is spread over a larger volume and is better stabilised : I⁻ $>$ Br⁻ $>$ Cl⁻ $>$ F⁻ in stability. The more stable the conjugate base, the stronger the acid, so acid strength is HF $<$ HCl $<$ HBr $<$ HI. For atoms in the same column, size matters more than electronegativity.