Explain the following with proper reasons :
(i) Fluorine cannot be prepared from fluorides by chemical oxidation.
(ii) Fluorine does not from `F_3^-` (polyhalide) ion

Explanation

(i)The standard reduction potential of fluorine is maximum .
`:underset(..)ddot(F).+e^(-) to :underset(..)ddot(F).^(-)`
Thus, it cannot be oxidised by any other reagent . `F^-` ion is very stable due to small size and high electronegativity of fluorine atom.
(ii)F- does not have empty d-orbital liked other halogen . The formation of `X_3^-` ions involves `sp^3d` hybridization.