Question

(a) Write down the electron arrangement in (i) a magnesium atom, and (ii) a chlorine atom.
(b) How many electrons are there in the valence shell of (i) a magnesium atom, and (ii) a chlorine atom?
(c) Show the formation of magnesium chloride from magnesium and chlorine by the transfer of electrons.
(d) State whether magnesium chloride will conduct electricity or not. Give reason for your answer.
(e) Why are covalent compounds generally poor conductors of electricity?

Answer 1

(a) (i) Magnesium atom contains 12 electrons.
Its electron arrangement can be written as $\stackrel{\mathrm{K}}{2}\stackrel{\mathrm{L}}{8}\stackrel{\mathrm{M}}{2}$.
(ii) Chlorine atom contains 17 electrons.
Its electron arrangement can be written as $\stackrel{\mathrm{K}}{2}\stackrel{\mathrm{L}}{8}\stackrel{\mathrm{M}}{7}$ .

(b) (i) Magnesium atom in its valence shell contains two electrons.
(ii) Chlorine atom in its valence shell contains seven electrons.

(c) In magnesium chloride molecule, magnesium atom transfers its two electrons to two chlorine atoms to form ionic bonds.


(d) Magnesium chloride will conduct electricity because it is an ionic compound. On melting or dissolving in water, it conducts electricity due to the separation of charged ions, which move freely across the solution.

(e) Covalent compounds are generally poor conductors of electricity because they do not contain ions that can move freely and pass electricity.