Question

(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?

Answer 1

(a)
(i) Sodium atom contains 11 electrons.
Its electronic configuration can be written as $\stackrel{\mathrm{K}}{2}\stackrel{\mathrm{L}}{8}\stackrel{\mathrm{M}}{1}$ .

(ii) Oxygen atom contains eight electrons.
Its electron arrangement can be written as $\stackrel{\mathrm{K}}{2}\stackrel{\mathrm{L}}{6}$ .

(b) (i) Sodium atom contains one electron in its outermost shell.
(ii) Oxygen atom contains six electrons in its outermost shell.

(c) In sodium oxide molecule, two sodium atoms transfer their one electron to one oxygen atom to form ionic bonds.


(d) Ionic compounds are generally hard because they consist of oppositely-charged ions. These ions are strongly attracted to each other and form a hard crystalline solid.

(e) The ionic compounds in solid state are bonded with strong intermolecular forces and are not free to move. Therefore, they cannot conduct electricity. However, when this salt melts, its constituent ions are separated from each other and become free to move across the melted salt that can conduct electricity.