Arrange the following in the order of property indicated set.
`F_(2),Cl_(2),Br_(2),I_(2)` in the increasing bond dissociation enthalpy.

Explanation

(i) The bond dissociation enthalpy of fluorine is lower than those of chlorine and bromine because the interelectronic replusion is very high. So, the order `I_(2)ltF_(2)ltBr_(2)ltCl_(2)` is the correct order of increasing bond dissociation enthalpy.
(ii) All the halogen acids ionise to give `H^(+)` ion and halide ion `X^(-)` (where, `X^(-)=F^(-),Cl^(-),Br^(-),I^(-)`). The bond in HI is weaker than those in HF, HCI and HBr, therefore HI is the strongest acid.
`HFltHClltHBrltHI` increasing acid strength
(iii) The size of a central atom of nitrogen is smaller than other given compounds and this property increases its basicity. Therefore, the correct order of increasing base strength is as follows:
`BiH_(3)ltSbH_(3)ltAsH_(3)ltPH_(3)ltNH_(3)`