The correct order of the thermal stability of hydrogen halides $(HX)$ is:

Identify the group of the periodic table that contains the element $Astatine$ $(At)$.

Arrange the following in the order of property indicated for each set:
$(i)$ $F_{2}, Cl_{2}, Br_{2}, I_{2}$ - increasing bond dissociation enthalpy.
$(ii)$ $HF, HCl, HBr, HI$ - increasing acid strength.
$(iii)$ $NH_{3}, PH_{3}, AsH_{3}, SbH_{3}, BiH_{3}$ - increasing base strength.

Which one of the following pairs of reactants does not form oxygen when they react with each other?

The correct statement$(s)$ about the oxoacids,$HClO_4$ and $HClO$,is(are):
$[A]$ $HClO_4$ is more acidic than $HClO$ because of the resonance stabilization of its anion.
$[B]$ $HClO_4$ is formed in the reaction between $Cl_2$ and $H_2O$.
$[C]$ The central atom in both $HClO_4$ and $HClO$ is $sp^3$ hybridized.
$[D]$ The conjugate base of $HClO_4$ is a weaker base than $H_2O$.

Bromine is obtained commercially from sea water by adding