Objectives

• Know how to name compounds

• Know how to write formulas

• Know how to work out how many of each atom there are in a compound, based on a formula

Compounds contain two or more different types of atom.

Atoms in compounds

The compound, water, exists as molecules.

Each water molecule consists of two hydrogen atoms joined to one oxygen atom.

Water is produced from the chemical reaction between hydrogen and oxygen.

Making a compound – water

Two hydrogen molecules react with one oxygen molecule to produce two molecules of water.

+H H

H HO O

hydrogen oxygen water+

Why does water have different properties to its elements?

Properties of a compound –

carbon dioxideA compound has different properties to the elements from which it is made because the atoms are joined differently.

+ O OC

Black solid used as

fuel.

Colourless gas in which many

substances burn.

Colourless gas used in fizzy

drinks and fire extinguishers.

+

carbon oxygen carbon dioxide+

Copper Element Mercury Element

Aluminium Element Oxygen Element

Water (H2O)

Iron sulphide (FeS)

Carbon dioxide (CO2)

To name simple compounds of metals and non-metals:

Naming simple compounds

2. Write down the name of the non-metal, changing the ending of the word to “-ide”.

1. Write down the name of the metal.

What is the name of the compound made when the following elements combine?

magnesium and oxygen

sodium and chlorine oxygen and iron

magnesium oxide

sodium chloride

iron oxide

What is the name of each compound formed by these metal and non-metal elements?

nitrogenlithium

sulphurzinciodinenickel

brominealuminium

oxygentin

chlorinesodiumnitrogenmagnesium

sulphuriron

Name of compoundElement2Element 1

iron sulphidemagnesium nitridesodium chloridetin oxide

aluminium bromidenickel

iodidezinc sulphidelithium nitride

Naming simple compounds

Many compounds contain more than two elements.

oxygenbrominealuminium

oxygensulphurcopper

oxygen

oxygen

oxygen

Element 3

nitrogensodium

magnesium nitratenitrogenmagnesium

nickel sulphatesulphurnickel

Name of compoundElement 2Element 1

sodium nitratecopper sulphatealuminium

bromate

Naming further compounds

For compounds containing two elements plus oxygen, the ending of the other non-metal usually changes to “--ate”.

A compound always contains a particular amount of each element. It has a fixed composition.

Composition of compoundsA compound contains atoms from different

elements that are chemically joined together.

Compound names can get quite long and complicated, so the symbols of the elements are used as a shorthand.The symbols of the elements in a compound are combined to give the formula of the compound.What is the formula of carbon dioxide?

carbon dioxide

A formula uses the symbols of the elements in a compound.

When there is more than one atom of each element, the number is always written after the symbol.

Writing a formula

carbon atom = 1formula =

hydrogen atoms = 2formula =

The formula shows the ratio of atoms in a compound.

water

CO2

H2O

oxygen atoms = 2

oxygen atom = 1

1. Titanium oxideFor every titanium atom there are two oxygen atoms.Formula =

2. Lithium oxide For every two lithium atoms there is one oxygen atom.

Formula =

3. Aluminium chloride For every aluminium atom there are three chlorine atoms.

Formula =

What is the formula of each of these compounds?

What is the formula?

TiO2

Li2O

AlCl3

(In a formula put the metal first as when naming a compound.)

1. Silicon chlorideFor every silicon atom there are four chlorine atoms.Formula =

2. Manganese oxide For every manganese atom there are two oxygen atoms.

Formula =

3. Aluminium oxide For every two aluminium atoms there are three oxygen atoms.

Formula =

What is the formula of each of these compounds?

What is the formula?

SiCl4

MnO2

Al2O3

(In a formula put the metal first as when naming a compound.)

What is the ratio of atoms?

What does a formula show?