(a) Show the formation of Na2O by the transfer of electrons between the combining atoms.
(b) Why are ionic compounds usually hard?
(c) why ionic compounds in the solid state do not conduct electricity and they do so when in molten state?
(b) These are relatively hard because these are present as aggregates of several positive and negative ions combined together by strong electrostatic forces.
(c) In solid state, ions in ionic compounds are not mobile while these become mobile in molten state.