Give reasons for the following:
$(i)$ Most metals conduct electricity well.
$(ii)$ The reaction of iron $(III)$ oxide,$Fe_{2}O_{3}$,with heated aluminium is used to join cracked machine parts.
$(iii)$ Sodium,potassium,and lithium are stored under oil.

(N/A) $(i)$ Metals conduct electricity because they possess free electrons that are mobile. Consequently,they offer minimal resistance to the flow of electric current.
$(ii)$ The reaction between iron $(III)$ oxide $(Fe_{2}O_{3})$ and aluminium is highly exothermic. The heat released is sufficient to produce molten iron,which fills the cracks in machine parts. This is known as the thermite reaction:
$Fe_{2}O_{3}(s) + 2Al(s) \xrightarrow{\text{Heat}} 2Fe(l) + Al_{2}O_{3}(s)$
$(iii)$ These metals are stored under oil for two primary reasons:
$(a)$ They are highly reactive and can spontaneously catch fire upon contact with atmospheric oxygen.
$(b)$ They react readily with moisture and carbon dioxide in the air,forming a layer of oxides or carbonates on their surface.