The magnitude of enthalphy of formation of alkali metal halides decreases in the order

Options

A. iodide `gt` bromide` gt `chloride `gt` fluoride
B. bromide gt iodide gt fluoride gt chloride
C. fluoride gt chloride gt iodide gt bromide
D. fluoride gt chloride gt bromide gt iodide

Answer

D

Explanation

For a given metal, `Delta_(f)H^(theta)` always becomes less negative from fluoride to iodide : `LiF(-612 "kJ mol"^(-1)), LiCI(-398), LiBr(-350), and LiI(-271)`. This is probably due to increasing polarizability of halide ion from `f^(-) "to" I^(-)`. Thus, fluorides are the most stable while iodides are the least stable.