Question

Give reasons for the following:
A.Aluminium oxide is considered as an amphoteric oxide
B.Ionic compounds conduct electricity in molten state

Answer 1

Hint: To answer this question, you must recall the relation of the electronegativities of atoms and the bond form between them. Greater is the difference in the electronegativities of the atoms, more is the chances for the formation of an ionic bond.

Complete answer:
(A) Aluminium oxide is an amphoteric oxide.
Aluminium oxide contains oxide ions and reacts with acids the same way alkali metal oxides and alkaline earth metal oxides do. Furthermore, it displays basic properties as well and reacts with bases like sodium hydroxide. Apart from the basic character shown by metal oxides, aluminium oxide also shows acidic character because the electronegativity difference between aluminium and oxygen is small. As a result, the aluminium atom holds on to the oxygen atom more strongly than expected and breaking of the bond is not very easy.
(B) To conduct electricity, a substance must have some sort of a charge carrier, which may be electrons or ions and there should be a way so that the charge carriers can move freely within the substance.
Ionic compounds consist of charged particles, i.e., cations and anions. There are a great number of free ions present in the molten state which are able to conduct electricity. In the molten state, the electrostatic forces of attraction that hold the oppositely charged ions together are overcome by the heat used to melt the solid giving free ions.

Note:
Ionic compounds do not conduct electricity in solid state as the movement of the ions is restricted. The ions are present at fixed positions and cannot move freely.