Draw the molecular formula and structure of perbromic acid.

The colour of the $X_2$ molecules of group $17$ elements changes gradually from yellow to violet down the group. This is due to
[$A$] the physical state of $X_2$ at room temperature changes from gas to solid down the group
[$B$] decrease in $HOMO-LUMO$ gap down the group
[$C$] decrease in $\pi^*-\sigma^*$ gap down the group
[$D$] decrease in ionization energy down the group

Which element from the following combines with hydrogen to form a compound having the lowest acidic strength?

Which of the following can chlorine not displace?

The correct order of acidic strength of oxy-acids of chlorine is

Among the following oxoacids,the correct decreasing order of acid strength is: