The oxides of Cl, Br and I are well known. They have various composition. The oxides are thermally unstable and dangerously explosive. They react with alkali. The bromine oxides are thermally more stable than chlorine oxides. The structure of halogen oxides is explained on the basis of VSEPR theory.
The hydrides of chlorine, bromine and iodine can be made by direct synthesis an they are well strongly fuming become increasingly more powerful reducing agents. Halogens also form oxoacids of the form `HOX,HXO_(2) ,HXO_(3) " and " HXO_(4)` The acidic character of oxoacids and halogen oxides decreases from 'Cl' to 'I', however it increases with increase in oxidation number of halogen in them.
Which of the following does not dimerise?

Explanation

(i) The potential difference between two electrodes can be determined by connecting them to a voltmeter therefore it is not possible to determine the potential of a single electrode because a single electro constitiues a half cell and a half cell reaction cannot take place independely
An electrode in a half cell cannot lose or gain electrons by itself for transfer of electrons one half cell to be connected to some other half cel thus we cannot determine the absolute value of electrode potential of a single eletrode the half cell with some standard electrode as the reference electrode
(ii) The electrode potential of iron `(E_(Fe^(2+)//Fe)^(@)=-0.44)` is lower than that of copper and hence Fe has greater tendency to get converted in to `Fe^(2+)` ions than Cu in other words undergoes oxidation more readily than copper
(iv) copper has lower electrode potential than silver therefore Cu releases electrons and tets oxidised to `Cu^(2+)` ions while `Ag^(+)` ions accept these electrons and get reduced to Ag metal
`Cu(s)+2Ag^(+)(aq)rarrCu^(2+)(aq)+2Ag(s)`
(v) Fe has lower electrode potential `(E_(Fe^(2+)//Fe)^(@)=-0.44)` than that of hydrogen therefore Fe is a better reducing agent than `H_(2)` and hence reduce `H^(+)` ions to produce `H_(2)` gas `Fe(s)+2H^(+)(a)rarrFe^(2+)(Aq)+H_(2)(g)`
In contrast s has higher electrode potential than hydrogen therefore `H_(2)` is a better reducing agent than ag in other words Ag cannot reduce to colourless `CI^(-)` ions while `I^(-)` ions get oxidised to violet coloured iondine
`CI_(2)(aq)+2I^(-)(aq)rarr2CI^(-)(aq)+I_(2)` (s)