Ionic Compounds

Question 1

Describe the structure of an ionic compound.

Answer 1

• There are strong electrostatic forces of attraction between the oppositely charged ions
• The forces act in all directions
• Ions bond together to form giant lattice structure

Question 2

Explain why ionic compounds have high melting and boiling points.

Answer 2

• This is due to the strong attractions between ions
• It takes a large amount of energy to break these forces

Question 3

Explain the electrical conductivity of ionic compounds.

Answer 3

• Solid ionic compounds don’t conduct electricity because the ions are in fixed positions and can’t move
• When molten or dissolved in water, ionic compounds conduct electricity because the ions are free to move and will carry a charge

Question 4

Explain the use of the endings –ide and –ate in the names of compounds.

Answer 4

The name of an ionic compound ends in:

• -ide if it contains just two elements
• -ate if it contains three or more elements, one of which is oxygen

Question 5

Give one advantage and one disadvantage of using a 2D representation of a molecule or compound.

Answer 5

Advantages

• Good at showing what atoms some substances contain
• Good at showing how atoms are connected

Disadvantages

• Doesn’t show the shape of a substance
• Doesn’t give any idea about the size of atoms

Question 6

Give one advantage and one disadvantage of using a ‘dot and cross diagram’ to represent a molecule or compound.

Answer 6

Advantages

• Useful for showing how compounds or molecules are formed
• Good at showing where electrons or ions in bonds came from

Disadvantage

• Doesn’t normally show anything about the size of atoms or how they’re arranged

Question 7

Give one advantage and one disadvantage of using a 3D model to represent a molecule or compound.

Answer 7

Advantage

• Shows the arrangement of ions in solids

Disadvantage

• Only shows the outer layer of a substance

Question 8

Give one advantage and one disadvantage of using a ‘ball and stick model’ to represent a molecule or compound.

Answer 8

Advantages

• Good for helping visualise structures
• Shows shape of lattice or molecule in 3D
• More realistic than 2D drawings

Disadvantages

• Misleading because it makes it seem like there are big gaps between atoms
• Doesn’t show correct scale of atoms or ions