Properties of Ionic Compounds

Question 1

What are ionic bonds?

Answer 1

strong electrostatic forces of attraction between oppositely charged ions

(for example Na⁺ and Cl⁻ ions attract each other)

Question 2

What structure is formed by ions in an ionic compound?

Answer 2

a (giant) lattice structure with:

• a regular arrangement of ions
• ionic bonds between oppositely charged ions

Question 3

Do ionic compounds usually have high or low melting/boiling points and why?

Answer 3

high

an ionic compound has a lot of strong ionic bonds between ions; it takes a lot of energy to break them, so it has a high melting/boiling point

(-there are many strong ionic bonds
-large amounts of energy must be transferred to the lattice structure to break these bonds)

Question 4

Are ionic compounds usually soluble?

Answer 4

yes, they dissolve to form aqueous solutions

Question 5

What state are ionic compounds at room temperature?

Answer 5

solid

Question 6

Aluminium oxide is an insoluble ionic compound.

(a) State why solid aluminium oxide cannot conduct electricity.
(b) Describe how you could make aluminium oxide conduct electricity.
(c) Suggest why the method described in (b) may be expensive.

Answer 6

(a) It has no free moving ions to carry charge; they are held in fixed positions and are not free to move.

(b) Heat it up until it is molten/a liquid.
(Aluminium oxide is not soluble)

(c) It requires a lot of energy, because aluminium oxide has a high melting point.

Question 7

(a) State why sodium chloride does not conduct electricity when it is in the solid state.
(b) Explain why sodium chloride does conduct electricity when it is molten or in aqueous solution?

Answer 7

(a) There are no free moving ions to carry charge, because ions can’t move around in a solid.
(b) It has free moving ions (because it is a liquid/dissolved in water) that can carry charge from place to place.