Explain the following:
$(a)$ $NaCl$ is not a conductor of electricity in solid state,whereas it does conduct electricity in aqueous solution as well as in molten state.
$(b)$ Iron articles are galvanised.
$(c)$ Metals like $Na, K, Ca$ and $Mg$ are never found in their free state in nature.

(A) In solid $NaCl$,the movement of ions is not possible due to its rigid structure. However,in aqueous solution or molten state,the electrostatic forces of attraction are overcome,allowing the ions to move freely and conduct electricity.
$(b)$ Iron articles are galvanised to protect them from corrosion (rusting). Galvanisation involves coating iron with a thin layer of zinc,which is more reactive than iron and prevents the iron from coming into contact with oxygen and moisture.
$(c)$ Metals like $Na, K, Ca$ and $Mg$ are highly reactive. They readily react with other elements such as oxygen,sulfur,and carbon present in the environment to form compounds like oxides,sulfides,or carbonates,and therefore are never found in their free elemental state in nature.