Recap, we have learnt

2 types of bonds exist between compounds

Covalent Bonds - Electrons are

shared

Ionic Bonds - Electrons are

Transferred

- Balancing charges

(D) Properties of Ionic Compounds:

1. made of crystals2. have high melting points3. often soluble in water4. conduct electricity in water

They are crystalline solids

2D Image

Why do ionic compounds have high melting points?

Opposite charges attract, forming strong ionic bonds.

Thus a lot of energy is needed to separate the ions.

Why do ionic compounds dissolve in water?

The electrons in H2O molecule are not evenly spread.One end of the molecule is slightly negative compared to the other end.

•The water molecules are attracted to the ions and pull them from the giant structure.

•The compound dissolves.

•Its ions are now free to move around able to conduct electricity.

Electrical Conductivity:

•Ionic compounds when solid do not conduct electricity.

•The ions are tightly held in place in the lattice structure and are unable to carry charges.

•However, when molten or dissolved in water, they can conduct electricity because the crystal lattice has broken down and the ions can move.

Do covalent compounds dissolve and conduct electricity too?

(D) Metallic Bonding

Metals generally have the following properties:

1. High melting and boiling points

2. Conduct electricity and heat

3. Hard and dense

4. Can be hammered into shapes (malleable)

5. Can be drawn out into wires (ductile)

Metal atoms (or ions) are held together by a sea of electrons.

Each metal atom gives up electrons from its outer shell into the sea or cloud of electrons.

These free electrons explain how electricity can pass through solid metals.

Lets Compare the 3 types of compounds – Covalent, Ionic & Metallic

Watch the video and answer these questions

Covalent Compound = Naphthalene

Ionic Compound = NaCl Metallic Compound = Tin

Questions : Copy these onto your notes

1. Which substance conducts electricity when solid?

2. Which substance conducts when dissolved in water?

3. Which substance does not dissolve in water?

Summary

Today we have touched on

The properties of ionic compoundsMetallic bonding (sea of electrons)Some differences between the 3 types of

compounds.