Q:

Writing Ionic Equation

According to the rules of writing ionic equation, only compounds in aqueous state can be split or dissociated into their ions, whereas elements or compounds in solid, liquid or gas state remain as they are. But what about molten sodium chloride which is NaCl(l) in liquid state, isn't it dissociated into ions when melted? So can we split it into its respective ions when writing ionic equations?

A:

The statement, "only compounds in aqueous state can be split or dissociated into their ions," is false in a number of ways.

As you state, molten salts are ionic, and there are room-temperature ionic liquids, such as ethylammonium nitrate , $\ce{(C2H5)NH3+·NO3-}$. 
In addition to water, there are other ionic solvents, such as nitromethane, $\ce{CH3NO2}$. Salts in these solvents break up to form ions.
Further, not everything dissolved in water is ionized. Sugar (sucrose), for example, is not ionized.

