Beryllium halides are covalent where as magnesium halides are ionic. Why?

Why do beryllium halides fume in air?

Aryl halides are less reactive than alkyl halides towards nucleophilic substitution reactions because of :

An example of halide ore is :

Alkyl halides on treatment with aqueous KOH give :

How alkyl halides are obtained from alcohols ?

Give an example for geminal halide.