What S the Pattern?

Studentactivity

Name ...... Class ...... Date ......

What’s the pattern?

Specification references:

• C2.1.2 Ionic bonding
• C2.1.3 Ionic compounds
• MS 5b

• WS 1.2

Aims

In this activity, you will look at ions and ionic bonding. The aim of this activity is to help you understand the link between an element’s position on the periodic table and the charge of its ion. This will help you in deducing the chemical formula of ionic compounds.

Learning outcomes

After completing this activity, you should be able to:

• give the charges of ions in Group 1, Group 2, Group 6, and Group 7 of the periodic table
• know that an ionic compound is a giant structure of ions arranged in a regular lattice
• represent the 3D structure of an ionic compound with a suitable model

• generate the formula of a wide range of ionic compounds when the charges of the ions are given.

Setting the scene

When a metal atom reacts with a non-metal atom, electrons in the outer shell of the metal are transferred to the non-metal. This turns the atoms into ions and an ionic compound is formed.

Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions, though the overall charge of the structure is zero. These forces act in all directions in the lattice and this is called ionic bonding.

Activity

In groups of three, take 20 sticky notes. Write the symbol for each of the first 20 elements on these sticky notes, each on a separate note (you’ll need a periodic table for this). Underneath the symbol for each element, also write the electronic structure of the atom, the electronic structure of its ion, and the charge of its ion.

Then, sort your sticky notes into groups based on the charge of the ion. What do you notice about these groups and how they compare to the periodic table? Discuss with your group what the position of an element in the periodic table tells you about the ion it will form.

Questions

Using the sticky notes and your own knowledge to help you, answer the following questions.

1Complete the following sentences:

When metals bond with non-metals, the metals ______electrons and become ______charged ions.

Non-metals ______electrons and become ______charged ions.

This type of bonding is called ______bonding.

The ions are held together by strong ______forces of attraction, which act in all directions.

2Suggest and explain why:

aGroup 0 elements do not form compounds.

bGroup 4 elements do not form ions.

Student follow up

1Ionic compounds have no overall charge.

aA calcium atom has 20 electrons and an oxygen atom has 8 electrons. Use the electronic structures of calcium and oxygen to deduce the ratio of calcium ions to oxygen ions in calcium oxide.

(2)

bA sodium atom has 11 electrons and a sulfur atom has 16 electrons. Use the electronic structures of sodium and sulfur to deduce the ratio of sodium ions to sulfur ions in sodium sulfide.

(2)

2The table below shows the formulae of some common ions

Three hydroxide ions (–1 charge) are needed to balance the charge of one aluminium ion (3 charge), so the chemical formula for aluminium hydroxide is Al(OH)3.

Use this information to work out the chemical formula of the following ionic compounds.

aLithium bromide

(1)

bSilver nitrate

(1)

cMagnesium chloride

(1)

dAluminium fluoride

(1)

eCopper sulfate

(1)

fPotassium carbonate

(1)

gChromium hydroxide

(1)

hMagnesium nitrate

(1)

iAluminium sulfate

(1)

© Oxford University Press 2016

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