Everything Science Grade 11

1.9 CHAPTER 1. ATOMICCOMBINATIONS

• Density
  Metals have a high density because their atomsare packed closely together.

Exercise 1 - 5

1. Give two examples of everyday objects that contain.

(a) covalent bonds

(b) ionic bonds

(c) metallic bonds

2. Complete the table which compares the different types of bonding:

Covalent Ionic Metallic

Types of atoms involved

Nature of bond betweenatoms

Melting Point (high/low)

Conducts electricity? (yes/no)

Other properties

3. Complete the table below by identifying thetype of bond (covalent,ionic or metallic) in each of
   the compounds:

Molecular formula Type of bond

H 2 SO 4

FeS

NaI

MgCl 2

Zn

Which of these substances will conduct electricity most effectively? Give a reason for your

answer.

4. Use your knowledgeof the different types ofbonding to explain the following statements:

(a) Swimming during alightning storm can be very dangerous.

(b) Most jewellery items are made from metals.

(c) Plastics are good insulators.

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1.9 Writing chemical formulae

The formulae of covalent compounds ESBR

To work out the formulae of covalent compounds, we need to use the valency of the atomsin the

compound. This is because the valency tells us how many bonds eachatom can form. This inturn