Name the halogen that does not undergo disproportionation. Write the reason. 

Explanation

Fluorine does not undergo disproportionation.
Fluorine exhibits only two oxidation numbers. Zero un uncombined state and -1 in compounds.
Reaction of white phosphorus in aqueous caustic soda solution, reaction of hot concentrated potash with bromine decomposition of manganese heptoxide to liberate oxygen, hydrolysis of dimeric sulphur monochloride and neutralisation of nitrogen dioxide with caustic soda solution are some examples of disproportionation reactions.
`P_(4) + 3NaOH + 3H_(2)O rarr PH_(3) + 3NaH_(2)PO_(2)`
`6KOH + 3Br_(2) rarr 5KBr + KBrO_(3) + 3H_(2)O`
`2Mn_(2)O_(7) rarr 4MnO_(2) = 3O_(2)`
`2S_(2)Cl_(2) + 2H_(2)O rarr 4HCl + SO_(2) + 3S`
`2NO_(2) + 2NaOH rarr NaNO_(2) + NaNO_(3) + H_(2)O`