IGCSEChemistry: Co-ordinated Sciences (Double Award)CIEExam QuestionsAtoms, Elements & CompoundsIons & Ionic Bonds

Ions & Ionic Bonds (CIE IGCSE Chemistry: Co-ordinated Sciences (Double Award))

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Ions & Ionic Bonds

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Ions & Ionic Bonds

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1a1 mark

Extended tier only

The diagrams below show the electron arrangement in two compounds.

kcl-and-h2o-electrons

In a water molecule, each hydrogen atom is bonded to the oxygen atom by sharing a pair of electrons.

Why does an oxygen atom share two pairs of electrons rather than just one pair?

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1b1 mark

Describe how a potassium atom becomes a potassium ion.

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1c1 mark

Why is there a bond between the ions in potassium chloride?

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1d2 marks

Extended tier only

Solid potassium chloride is a poor conductor of electricity. When dissolved in water it is a good conductor. Explain

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2a5 marks

The following is a list of the electron distributions of atoms of unknown elements.

element electron distribution
A 2,5
B 2,8,4
C 2,8,8,2
D 2,8,18,8
E 2,8,18,8,1
F 2,8,18,18,7

Choose an element from the list for each of the following descriptions.

i)
It is a noble gas.

ii)
II is a soft metal with a low density.

iii)
It can form a covalent compound with element A.

iv)
It has a giant covalent structure similar to diamond.

v)
It can form a negative ion of the type X3-.

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2b5 marks

Elements C and F can form an ionic compound.

i)
Draw a diagram that shows the formula of this compound, the charges on the ions and the arrangement of the valency electrons around the negative ion.

Use x to represent an electron from an atom of C.
Use o to represent an electron from an atom of F.
[3]

ii)
Predict two properties of this compound.
[2]

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3a3 marks

Magnesium reacts with bromine to form magnesium bromide.

Magnesium bromide is an ionic compound. Draw a diagram that shows the formula of the compound, the charges on the ions and the arrangement of outer electrons around the negative ion.
The electron distribution of a bromine atom is 2, 8, 18, 7.

Use x to represent an electron from a magnesium atom.
Use o to represent an electron from a bromine atom.

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3b7 marks

Extended tier only

In the lattice of magnesium bromide, the ratio of magnesium ions to bromide ions is 1:2.

i)
Explain the term lattice.
.[2]
ii)
Explain why the ratio of ions is 1:2.
[1]
iii)
The reaction between magnesium and bromine is redox. Complete the sentences.

Magnesium is the .................................... agent because it has .................................... electrons.

Bromine has been  ..................................... because it has  .................................... electrons.
[4]

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4a3 marks

Extended tier only

The structure of a typical ionic compound is a regular arrangement of positive and negative ions.

1REj6~tm_ionic-lattice

i)
What is the name of this regular arrangement of particles?

[1]

ii)
Give two physical properties of ionic compounds.
[2]

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4b4 marks

Extended tier only

Ions are formed by electron loss or gain. The electron distribution of a magnesium atom is 2 + 8 + 2 and of a nitrogen atom is 2 + 5.

i)
Give the formula of the magnesium ion.
[1]
ii)
Give the formula of the nitride ion.
[1]
iii)
What is the formula of the ionic compound, magnesium nitride?
[1]
iv)
In this compound there is an ionic bond. Why are the two ions attracted to each other?
[1]

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5a
Sme Calculator6 marks

The table below gives the number of protons, neutrons and electrons in atoms or ions.

Complete the table. The first line is given as an example.

You will need to use the Periodic Table.

particle number of protons number of electrons number of neutrons symbol or formula
A 4 4 5 Be presubscript 4 presuperscript 9
B 19 18 20  
C 30 30 35  
D 8 10 8  
E 31 31 39  

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5b3 marks

Using the data in the table, explain how you can determine whether a particle is an atom, a negative ion or a positive ion.

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6a1 mark

A list of symbols and formulae is shown.


CH4
Cl –
CO2
Cr3+
Cu2+
Fe2+
H2
K+
N2
O2
SO2

Which symbol or formula represents an ion formed when an atom gains an electron?

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6b5 marks

The diagram shows part of the structures of caesium chloride and carbon dioxide.

YQBw3c9A_q8_0620-s20-qp-32_cie-igcse-chemistry

Describe both caesium chloride and carbon dioxide in terms of:

  • bonding
  • arrangement of particles.

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6c1 mark

The diagrams show part of the structures of five substances, A, B, C, D and E.

__HfDsCS_q1-0620_s19_qp_32

State which one of these structures, A, B, C, D or E is an ionic compound.

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6d1 mark

begin mathsize 14px style Na presubscript 11 presuperscript 22 end style, begin mathsize 14px style Na presubscript 11 presuperscript 23 end style and begin mathsize 14px style Na presubscript 11 presuperscript 24 end style are isotopes of sodium.

Why do sodium ions have a charge of +1?

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16 marks

Extended tier only

Potassium iodide is an ionic compound. 

i)
Describe what happens, in terms of electron loss and gain, when a potassium atom reacts with an iodine atom.
[2]
ii)
Describe the structure of solid potassium iodide. You may draw a diagram.

[2]

iii)
Explain why potassium iodide has a high melting point.
[2]

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2a1 mark

Extended Only

Iron pyrite, FeS2, is known as Fool’s Gold because it is a shiny yellow solid which is similar in appearance to gold. Iron pyrite is an ionic compound. Gold is a metallic element.

Iron pyrite, FeS2, contains positive and negative ions. The positive ion is Fe2+. Deduce the formula of the negative ion.

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2b2 marks

A student is provided with a sample of iron pyrite and a sample of gold. Suggest how the student could distinguish between the two substances.

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3a4 marks

Nitrogen can form ionic compounds with reactive metals and covalent compounds with non-metals.

Nitrogen reacts with lithium to form the ionic compound lithium nitride, Li3N.

i)
Write the equation for the reaction between lithium and nitrogen.

[2]

ii)
Lithium nitride is an ionic compound. Draw a diagram which shows its formula, the charges on the ions and the arrangement of the valency electrons around the negative ion.

Use x for an electron from a lithium atom.
Use o for an electron from a nitrogen atom.

[2]

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3b4 marks

Nitrogen fluoride is a covalent compound.

i)
Draw a diagram showing the arrangement of the valency electrons in one molecule of the covalent compound nitrogen trifluoride, NF3.

Use x for an electron from a nitrogen atom.
Use o for an electron from a fluorine atom.

[2]

ii)
Lithium nitride has a high melting point, 813 °C. Nitrogen trifluoride has a low melting point, –207 °C.

Explain why the melting points are different.

[2]

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4a4 marks

The Group I metals show trends in both their physical and chemical properties.

i)
How do their melting points vary down the Group?

[1]

ii)
Which element in the Group has the highest density?

[1]

iii)
All Group I metals react with cold water. Complete the following equation.

........Rb + ........H2O → ................ + ................

[2]

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4b5 marks

Extended tier only

Lithium reacts with nitrogen to form the ionic compound, lithium nitride.

i)
State the formula of the lithium ion.

[1]

ii)
Deduce the formula of the nitride ion.

[1]

iii)
In all solid ionic compounds, the ions are held together in a lattice.
Explain the term lattice.

[1]

iv)
What is the ratio of lithium ions to nitride ions in the lattice of lithium nitride?
Give a reason for your answer.

[2]

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5a2 marks

Table 1.1 shows the properties of four substances.

Table 1.1

substance boiling point electrical
conductivity of solid		 electrical conductivity
when molten		 density
in g / cm3
aluminium high conducts conducts 2.70
diamond       3.51
potassium bromide high does not conduct conducts 2.75
sulfur low does not conduct    

State the meaning of the term ionic bonding.

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5b2 marks

Identify which information in Table 1.1 shows that potassium bromide is an ionic compound.

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5c3 marks

Magnesium, calcium and strontium are Group II elements

Magnesium reacts with chlorine to form magnesium chloride, MgCl2.

Magnesium chloride is an ionic compound.

Complete the dot-and-cross diagram in Figure 1.1 of the ions in magnesium chloride.

Show the charges on the ions.

Figure 1.1

q2d_specimen-paper-0620-04-cie-igcse-chemistry-p

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5d2 marks

One physical property typical of ionic compounds, such as MgCl2, is that they are soluble in water.

Give two other physical properties that are typical of ionic compounds.

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6a3 marks

Fluorine forms both ionic and covalent compounds.

Magnesium reacts with fluorine to form the ionic compound magnesium fluoride.

The electronic structures of an atom of magnesium and an atom of fluorine are shown.

q2a-0620-s20-qp-42

Complete the dot-and-cross diagrams to show the electronic structures of one magnesium ion and one fluoride ion.

Show the charges on the ions.

q2ai-0620-s20-qp-42

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6b2 marks

Extended tier only

Magnesium fluoride does not conduct electricity when it is solid.

What can be done to solid magnesium fluoride to make it conduct electricity?

In your answer explain why magnesium fluoride conducts electricity when this change is made.

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6c2 marks

Extended tier only

The melting points of magnesium fluoride and carbonyl fluoride are shown.

  melting point / °C
magnesium fluoride  1263
carbonyl fluoride  −111

Explain, using your knowledge of structure and bonding, why magnesium fluoride has a high melting point.

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7a3 marks

Magnesium exists as three isotopes, Mg presubscript 12 presuperscript 24, Mg presubscript 12 presuperscript 25 and Mg presubscript 12 presuperscript 26.

Magnesium reacts with oxygen to form the ionic compound magnesium oxide.

Complete the dot-and-cross diagrams to show the electronic structures of the ions in magnesium oxide.

Show the charges on the ions.

q2di-0620_s19_qp_43

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7b1 mark

Extended tier only

Magnesium oxide melts at 2853 °C.

Why does magnesium oxide have a high melting point?

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7c1 mark

Extended tier only

Explain why molten magnesium oxide can conduct electricity.

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1a
Sme Calculator3 marks

The first three elements in Period 6 of the Periodic Table of the Elements are caesium, barium and lanthanum.

How many more protons, electrons and neutrons are there in one atom of lanthanum than in one atom of caesium. Use your copy of the Periodic Table of the Elements to help you.

Number of protons =

Number of electrons = 

Number of neutrons =

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1b4 marks

Extended Only

All three metals can be obtained by the electrolysis of a molten halide. The electrolysis of the aqueous halides does not produce the metal.

i)
Complete the equation for the reduction of lanthanum ions at the negative electrode (cathode).

La3+ + ................ → ................

[1]

ii)
Name the three products formed by the electrolysis of aqueous caesium bromide.

[3]

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1c2 marks

All three metals react with cold water. Complete the word equation for these reactions.

metal + water → ................................. + .............................

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1d2 marks

Barium chloride is an ionic compound. Draw a diagram that shows the formula of the compound, the charges on the ions and gives the arrangement of the valency electrons around the negative ion.

The electron distribution of a barium atom is 2.8.18.18.8.2

Use x to represent an electron from a barium atom.
Use o to represent an electron from a chlorine atom.

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1e2 marks

Extended Only 

Describe, by means of a simple diagram, the lattice structure of an ionic compound, such as caesium chloride.

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1f4 marks

Extended Only 

The reactions of these metals with oxygen are exothermic.  

2Ba (s) + O2 (g) → 2BaO (s)

i)
Give an example of bond forming in this reaction.

[1]

ii)
Explain using the idea of bond breaking and forming why this reaction is exothermic.

[3]

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2a3 marks

Calcium reacts with nitrogen to form the ionic compound calcium nitride, Ca3N2.

Draw a diagram, based on the correct formula, which shows the charges on the ions and the arrangement of the electrons around the negative ion.

Use o to represent an electron from a calcium atom.
Use x to represent an electron from a nitrogen atom.

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2b4 marks

Extended tier only

In the lattice of calcium nitride, the ratio of calcium ions to nitride ions is 3 : 2.

i)
What is meant by the term lattice?

[2]
ii)
In terms of ionic charges, explain why the ratio of ions is 3 : 2.

 [2]

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2c3 marks

Extended tier only

The reaction between calcium and nitrogen to form calcium nitride is a redox reaction. In terms of electron transfer, explain why calcium is the reducing agent.

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3a6 marks

Extended tier only

The diagram shows the lattice of a typical ionic compound.

ionic-lattice

i)
Explain the term ionic lattice.

[2]

ii)
In this lattice, the ratio of positive ions to negative ions is 1:1.
In the lattice of a different ionic compound, the ratio of positive ions to negative ions is 1:2.
Suggest why this ratio varies in different ionic compounds.

 [1]

iii)
Give three physical properties of ionic compounds.

[3]

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3b3 marks

Extended tier only

Strontium oxide is an ionic compound.

Draw a diagram which shows its formula, the charges on the ions and the arrangement of the valency electrons around the negative ion.

The electron distribution of a strontium atom is 2 + 8 + 18 + 8 + 2.
Use o to represent an electron from a strontium atom.
Use x to represent an electron from an oxygen atom.

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44 marks

Extended tier only

The structure of an element or compound determines its physical properties.
Scandium fluoride and silicon(IV) oxide have giant structures.

Scandium fluoride is an ionic compound.

i)
The valency of scandium is three.
Draw a diagram which shows the formula of the compound, the charges on the ions and the arrangement of the valency electrons around the negative ion.

Use x to represent an electron from a scandium atom.
Use o to represent an electron from a fluorine atom.
[3]
ii)
The melting point of scandium fluoride is 1552 °C. Explain why scandium fluoride has a high melting point.
[1]

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5a7 marks

Extended tier only

Both strontium and sulfur have chlorides of the type XCl2. The table below compares some of their properties.

  strontium chloride sulfur chloride 
 appearance white crystals red liquid
 formula SrCl2 SCl2
 melting point / oC 874 -120
 boiling point / oC 1250 59
 conductivity of liquid good poor
 solubility in water dissolves to form a neutral solution reacts to form a solution of pH 1

i)
Use the data in the table to explain why sulfur chloride is a liquid at room temperature, 25 °C.
[2]
 
ii)
Strontium is a metal and sulfur is a non-metal. Explain why both have chlorides of the type XCl2.
The electron distribution of a strontium atom is 2 + 8 + 18 + 8 + 2.
[2]

iii)
Explain the difference in the electrical conductivity of liquid strontium chloride and liquid sulfur chloride.
[3]

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5b3 marks

Strontium chloride-6-water can be made from the insoluble compound, strontium carbonate, by the following reactions.

SrCO3 (s) + 2HCl (aq) → SrCl2 (aq) + CO2 (g) + H2O (l)

SrCl2 (aq) + 6H2O (l) → SrCl2.6H2O (s)

The following method was used to prepare the crystals.

1.  Add excess strontium carbonate to hot hydrochloric acid.
2.  Filter the resulting mixture.
3.  Partially evaporate the filtrate and allow to cool.
4.  Filter off the crystals of SrCl2.6H2O.
5.  Dry the crystals between filter papers.

i)
How would you know when excess strontium carbonate had been added in step 1?
[1]
ii)
Why is it necessary to filter the mixture in step 2?
[1]
iii)
In step 3, why partially evaporate the filtrate rather than evaporate to dryness?
[1]

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