Ionic bonding (Edexcel IGCSE Chemistry (Modular): Unit 2)

This question is about sodium oxide, Na₂O

The diagram shows the electronic configuration of atoms of sodium and oxygen.

Sodium	Oxygen

Describe the changes in the electronic configuration of the atoms of sodium and oxygen to form the ions in sodium oxide.

Calculate the relative formula mass (M_r) of sodium oxide, Na₂O, using information from the Periodic Table.

 M_r = ..............................

Explain why solid sodium oxide does not conduct electricity.

Give a test to show that sodium oxide contains sodium ions.

When sodium oxide is heated it reacts to form sodium metal and sodium peroxide, Na₂O₂

Complete the equation for this reaction.

  Na₂O →

What is the formula of potassium sulfate?

The formation of ions and covalent bonds involves electrons. The table gives the electronic configurations of atoms of hydrogen, lithium and chlorine. 

Describe the different roles of electrons in the formation of

• ions in lithium chloride

• covalent bonds in hydrogen chloride

Explain why lithium chloride has a higher melting point than hydrogen chloride.

Refer to structure and bonding in your answer.

Which of the following dot-and-cross diagrams shows the correct arrangement of electrons in lithium sulfide?

This is a question about metals and their compounds.

State one property of metals.

Mercury is the only metal that is liquid at room temperature.

Describe the difference in the movement of particles in liquid mercury and in a solid metal.

Magnesium is a metal that burns in air.

 i) State one observation made during the combustion of magnesium metal.

 (1)

 ii) State one chemical property of the product of combustion that can be used to classify magnesium as a metal.

 (1)

In the absence of air, magnesium reacts with sulfur to form the ionic compound magnesium sulfide, MgS

 i) Give a reason why the reaction needs to be done in the absence of air.

 (1)

 ii) Describe, in terms of electrons, the formation of the ions in magnesium sulfide.

 Give the charges on the ions.

 (3)

 iii) Explain why magnesium sulfide has a very high melting point.

 (3)

 iv) Magnesium sulfide reacts with hydrochloric acid to form magnesium chloride and hydrogen sulfide gas, H₂S

 Give the chemical equation for this reaction.

 (2)

The diagram shows the electronic configurations of an atom of lithium and an atom of oxygen.

Which statement is not correct about the changes in electronic configuration that occur when lithium and oxygen react to form lithium oxide, Li₂O?

This question is about ionic compounds.

The table shows the formulae of some positive and negative ions, and the formulae of some compounds containing these ions.

i) Complete the table by giving the three missing formulae.

(3)

ii) Give the name of the compound with the formula NH₄NO₃

(1)

Sodium oxide, Na₂O, is an ionic compound. The sodium and oxide ions are held together by ionic bonds.

i) State the meaning of the term ionic bond.

(2)

ii) The diagram shows the arrangement of the electrons in a sodium atom and in an oxygen atom.

Draw diagrams in the boxes to show the arrangement of the electrons in the ions of sodium oxide.  Include the charges on the ions.

(3)

The diagram shows the arrangement of electrons in an atom of calcium and in an atom of chlorine.

Describe, in terms of electrons, what happens when calcium reacts with chlorine to form the ionic compound calcium chloride, CaCl₂

Describe tests to show that an aqueous solution of calcium chloride contains calcium ions and chloride ions.

calcium ions: ...................................................................... chloride ions:  ......................................................................

Solid calcium chloride does not conduct electricity. Aqueous solutions of calcium chloride do conduct electricity. A student uses this method to investigate how the conductivity of a solution changes when calcium chloride is dissolved in pure water.

• Step 1 add 100 cm³ of pure water to a beaker

• Step 2 add one spatula of solid calcium chloride to the beaker

• Step 3 stir the solution

• Step 4 measure the conductivity of the solution

• Step 5 repeat until nine spatulas of solid calcium chloride have been added

  The table shows the student’s results.

i) Plot the results on the grid and draw two straight lines of best fit. Ignore the anomalous result.

(3)

ii) State the trend shown on the graph for the first six spatulas of calcium chloride.

(1)

iii) Suggest an error the student could have made to cause the anomalous result.

(1)

Describe another way to make solid calcium chloride conduct electricity.

This question is about the halogens and their compounds.

The table gives the colour and physical state at room temperature of the halogens. Complete the table by predicting the colour of astatine and the physical state of fluorine at room temperature.

Chlorine gas is bubbled into a colourless solution of potassium bromide.

Explain why the solution turns orange.

Potassium bromide is an ionic compound.

Draw diagrams to show the outer electrons in a potassium ion and in a bromide ion.

Include the charges on the ions.

Separate: Chemistry Only

A student sets up a circuit to test the electrical conductivity of water, solid sodium chloride and aqueous sodium chloride.

The table shows the student’s results.

Explain these results, with reference to the structure and bonding of the substances.

Separate: Chemistry Only

A concentrated aqueous solution of sodium chloride is electrolysed using graphite electrodes.

Chlorine is formed at the positive electrode (anode).

i) Give an ionic half-equation for the formation of chlorine at the positive electrode.

(1)

ii) State why this ionic half-equation represents an oxidation reaction.

(1)

iii) Which substance is formed at the negative electrode (cathode)?

(1)

The diagram shows how the electrons are arranged in an atom of sulfur. Sulfur can form both covalent and ionic compounds. 

The electronic configuration of a sodium atom is 2.8.1 Sodium sulfide, Na₂S, is an ionic compound formed when sodium reacts with sulfur.

Describe, in terms of electrons, what happens when sodium sulfide is formed in this reaction.

Draw a dot-and-cross diagram to show the bonding in sodium sulfide.

Sodium sulfide is a water-soluble compound. When hydrogen sulfide gas is bubbled through sodium hydroxide it will form sodium sulfide and water. Explain why the melting point of hydrogen sulfide is lower than the melting point of sodium sulfide.

Write a balanced symbol equation including state symbols for the reaction occurring in part c).

This question is about chemical bonds.

Aluminium and chlorine react to form aluminium chloride. 

Write the balanced symbol equation for the reaction.  

Include state symbols. 

Describe, in terms of electron arrangement, the type of bonding in a molecule of chlorine. 

Describe, in terms of electron arrangement, the type of bonding in the compound aluminium chloride. 

Explain why molten aluminium chloride can conduct electricity.