Give reason for the following:

(a)(i) Ionic compounds have high melting and boiling points. (ii) Ionic compound is soluble in water. (iii) Ionic compounds conduct electricity in molten state. (b) Show the formation of MgO by transfer of electrons.

(a) (i) Ionic compounds have high melting and boiling points.

In ionic compounds, the ionic bonds are formed by exchange of electrons. There is strong electrostatic force of attraction between the two oppositely charged ions and give rise to strong ionic bond. Hence it requires high energy to break their strong ionic bonds. Hence ionic compounds have high melting and boiling points.

(ii) Ionic compound is soluble in water.

Ionic compounds are soluble in water, because in aqueous solution ionic compounds dissociate and produce positively charged cations and negatively charged anions.

(iii) Ionic compounds conduct electricity in molten state.

In aqueous solution or molten state ionic compounds dissociates to produce positively charged cations and negatively charged anions and they move towards oppositely charged electrodes. These charged particles or ions are capable to conduct electricity in molten state.

(b) Show the formation of MgO by transfer of electrons.

The atomic number of Mg = 12.

The electronic configuration = 2,8,2

Magnesium gives up 2 electrons and form Mg⁺⁺

Mg + 2e^-→ Mg⁺⁺

The atomic number of oxygens = 8

The electronic configuration = 2,6

Oxygen takes up 2 electrons and form O2^- + 2e^-→ O^2-

The oppositely charged Mg⁺⁺ and O2^- are held together by a strong electrostatic force of attraction and form MgO.

Mg⁺⁺ + O^2-→ MgO