(a) What is the electronic configuration of (i) a sodium atom, and (ii) an oxygen atom?
(b) What is the number of outermost electrons in (i) a sodium atom, and (ii) an oxygen atom?
(c) Show the formation of Na2O by the transfer of electrons between the combining atoms.
(d) Why are ionic compounds usually hard?
(e) How is it that ionic compounds in the solid state do not conduct electricity but they do so when in molten state?
(a) (i) 2, 8, 1 (ii) 2, 6
(b) (i) 1 (ii) 6
(c) figure.png
(d) Ionic compounds are usually hard because their oppositely charged ions attract one another strongly and form a regular crystal structure.
(e) Although solid ionic compounds are made up of ions but they do not conduct electricity in solid state. This is because in the solid ionic compound the ions are held together in fixed positions by strong electrostatic forces and cannot move freely. However, when we dissolve the ionic solid in water or melt it, the crystal structure is broken down and ions become free to move and conduct electricity. Thus, an aqueous solution of an ionic compound conducts electricity because there are plenty of free ions in the solution which are able to conduct electric current.