Edexcel A-Level Chemistry AS 3 Bonding and Structure Questions

Identify the bonding and particles present, draw or interpret the requested representation and connect charge, geometry or intermolecular attraction to the observed property.

Exam points

Draw electron, ionic-lattice or molecular diagrams with correct charges and bonding.
Predict molecular shape and bond angle from electron-pair arrangement and repulsion.
Explain structure and properties through bonding, polarity and intermolecular forces.

Covered syllabus points

3.1—Interpret evidence for the existence of ions 3.2—The formation of ions in terms of loss or gain of electrons 3.3—Draw dot-and-cross diagrams to show electrons in cations and anions 3.4—Ionic crystals as giant lattices of ions 3.5—Ionic bonding is the result of strong net electrostatic attraction between ions 3.6—The effects of ionic radius and ionic charge on the strength of ionic bonding 3.7—Reasons for the trends in ionic radii down a group in the Periodic Table, and for a set of isoelectronic ions 3.8—The meaning of the term ‘polarisation’ as applied to ions 3.9—The polarising power of a cation depends on its radius and charge, and the polarisability of an anion also depends on its 3.10—Covalent bonding is the strong electrostatic attraction between two nuclei and the shared pair of electrons between them 3.11—Draw dot-and-cross diagrams to show electrons in covalent substances 3.12—The different structures formed by giant lattices of carbon atoms 3.13—The meaning of the term ‘electronegativity’ as applied to atoms in a covalent bond 3.14—Ionic and covalent bonding are the extremes of a continuum of bonding type 3.15—Distinguish between polar bonds and polar molecules and predict whether or not a given molecule is likely to be polar 3.16—The principles of the electron-pair repulsion theory, used to interpret and predict the shapes of simple molecules and ions 3.17—The terms ‘bond length’ and ‘bond angle’3.18—And explain the shapes of, and bond angles in, BeCl2, BCl3, CH4, NH3, NH4+, H2O, CO2, gaseous PCl5, SF6 and C2H4 3.19—Apply the electron-pair repulsion theory to predict the shapes of, and bond angles in, molecules and ions analogous to those 3.20—Metals consist of giant lattices of metal ions in a sea of delocalised electrons 3.21—Metallic bonding is the strong electrostatic attraction between metal ions and the delocalised electrons 3.22—The models in 3.20 and 3.21 to interpret simple properties of metals

[Maximum number: 6]

This question is about magnesium, magnesium oxide and magnesium sulfate.

(a)

Magnesium oxide and magnesium sulfate are ionic compounds.

[ 4 ]

(i)

Draw a dot-and-cross diagram to show the bonding in magnesium oxide, MgO .
Show outer electrons only.

[ 2 ]

(ii)

The melting temperatures of magnesium oxide and magnesium sulfate are $2852^{\circ} \mathrm{C}$ and $1124^{\circ} \mathrm{C}$ respectively.

Explain why the melting temperature of magnesium oxide is significantly higher than that of magnesium sulfate.

[ 2 ]

An answer that makes reference to the following points:

- oxide/ $\mathrm{O}^{2-}$ smaller than sulfate/ $\mathrm{SO}_{4}{ }^{2-}$

- stronger (electrostatic) attraction between the ( $\mathrm{Mg}^{2+}$ and $\mathrm{O}^{2-}$ ) ions

Allow just the oxide is smaller or vice versa Do not award comparison with sulfur or sulfide

Allow stronger ionic bond

Allow more energy required to break the ionic bond

Allow reverse argument Ignore reference to lattice energy Ignore reference to distortion/polarisation Any reference to intermolecular forces /covalent bond/molecular structure score 0

(2)

(b)

The table gives some data about the electrical conductivity of magnesium and magnesium oxide.

Table for Question (b) — Edexcel A-Level Chemistry AS

Explain the similarities and differences in the electrical conductivity of the two substances.

[ 2 ]

[Maximum number: 9]

The radii of ions of some successive elements in the Periodic Table are shown.

Table for Question 2 — Edexcel A-Level Chemistry AS

(a)

Explain the trend in the ionic radii from the nitride ion to the aluminium ion.

[ 3 ]

(b)

Sodium and fluorine react to form a compound.

[ 6 ]

(i)

State the structure and bonding of sodium fluoride.

[ 1 ]

(ii)

Explain how the electrical conductivity of sodium fluoride provides evidence for the existence of ions.

[ 3 ]

(iii)

Explain why the fluoride ion is difficult to polarise.

[ 2 ]

[Maximum number: 5]

Mohr's salt, $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{Fe}\left(\mathrm{SO}_{4}\right)_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}$ , and copper(II) chromate(VI) are both ionically-bonded solids.

(a)

State what is meant by the term 'ionic bond'.

[ 1 ]

(b)

Electrolysis is an experiment which can be carried out in a school or college laboratory on an aqueous green solution of copper(II) chromate(VI) to provide evidence for the presence of ionic bonding.

Draw a labelled diagram in the Answer Book of the apparatus that you would use for this experiment.
Indicate observations which show that the bonding in copper(II) chromate(VI) is ionic.

[ 4 ]

[Maximum number: 2]

This question is about magnesium, magnesium oxide and magnesium sulfate.

The table gives some data about the electrical conductivity of magnesium and magnesium oxide.

Table for Question 4 — Edexcel A-Level Chemistry AS

Explain the similarities and differences in the electrical conductivity of the two substances.

[Maximum number: 2]

This question is about magnesium, magnesium oxide and magnesium sulfate.

Magnesium oxide and magnesium sulfate are ionic compounds.

Draw a dot-and-cross diagram to show the bonding in magnesium oxide, MgO .
Show outer electrons only.

[Maximum number: 1]

The radii of ions of some successive elements in the Periodic Table are shown.

Table for Question 6 — Edexcel A-Level Chemistry AS

Sodium and fluorine react to form a compound.

State the structure and bonding of sodium fluoride.

[Maximum number: 1]

Mohr's salt, $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{Fe}\left(\mathrm{SO}_{4}\right)_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}$ , and copper(II) chromate(VI) are both ionically-bonded solids.

State what is meant by the term 'ionic bond'.

[Maximum number: 2]

This question is about magnesium, magnesium oxide and magnesium sulfate.

Magnesium oxide and magnesium sulfate are ionic compounds.

[Maximum number: 3]

The radii of ions of some successive elements in the Periodic Table are shown.

Table for Question 9 — Edexcel A-Level Chemistry AS

Explain the trend in the ionic radii from the nitride ion to the aluminium ion.

[Maximum number: 2]

The radii of ions of some successive elements in the Periodic Table are shown.

Table for Question 10 — Edexcel A-Level Chemistry AS

Sodium and fluorine react to form a compound.

Explain why the fluoride ion is difficult to polarise.

[Maximum number: 1]

This question is about the bonding in the elements of Period 3 in the Periodic Table. The melting temperatures of the Period 3 elements are shown in the table.

Table for Question 11 — Edexcel A-Level Chemistry AS

In the elements silicon, phosphorus, sulfur and chlorine, the atoms are joined by covalent bonds.

Describe the attraction between the atoms in a covalent bond.

[Maximum number: 2]

Chlorine dioxide, $\mathrm{ClO}_{2}$ , can be used to treat water to make it safe for drinking. The molecule is a free radical. One suggested structure is shown.

Figure for Question 12 — Edexcel A-Level Chemistry AS

Complete the dot-and-cross diagram for this structure. Use dots (•) for oxygen electrons and crosses (×) for chlorine electrons.

[Maximum number: 1]

The elements carbon and silicon both form dioxides.

The structure of silicon dioxide may be referred to as a diamond structure.

Figure for Question 13 — Edexcel A-Level Chemistry AS

silicon
- oxygen

Using your knowledge of the structure of diamond, suggest how the structure of silicon dioxide is similar to that of diamond.

[Maximum number: 1]

This question is about the elements in Group 7.

State the meaning of the term electronegativity.

[Maximum number: 2]

The elements carbon and silicon both form dioxides.

The shape of the carbon dioxide molecule affects its physical properties.

Explain the polarity of the carbon-oxygen bond.

An explanation that makes reference to the following points:

- the carbon atom is slightly positive $/ \delta+$ and the oxygen atom slightly negative / δ-

- because oxygen is more electronegative than carbon

Accept shown on a diagram e.g.

Figure for Answer to Question 15 — Edexcel A-Level Chemistry AS

Accept reverse argument

Ignore "they have different electronegativities"

[Maximum number: 3]

This question is about alkenes.

Another compound, Y, has the structure shown.

Figure for Question 16 — Edexcel A-Level Chemistry AS

A student stated that
‘Compound Y has polar bonds so it is a polar molecule’.
Comment on this statement.

[Maximum number: 1]

Chlorine dioxide, $\mathrm{ClO}_{2}$ , can be used to treat water to make it safe for drinking. The molecule is a free radical. One suggested structure is shown.

Figure for Question 17 — Edexcel A-Level Chemistry AS

Give the reason why chlorine dioxide is not a linear molecule.

[Maximum number: 3]

The elements carbon and silicon both form dioxides.

The shape of the carbon dioxide molecule affects its physical properties.

Explain the shape of the carbon dioxide molecule.

An explanation that makes reference to the following points:

- there are two sets of bonding electrons (and no lone pairs) about the carbon atom

- which arrange to minimise repulsion (1)

- resulting in a linear shape / bond angle of $180^{\circ}$ (1)

Any indication of two regions of electrons (this includes a correct diagram) e.g. O=C=O

Allow two double bonds

Allow maximum separation / to be as far apart as possible

Accept bond angle labelled on a diagram

Ignore references to symmetry Ignore references to lone pairs on oxygen

All marks are independent

No TE for any mark

[Maximum number: 3]

This question is about ethene, $\mathrm{C}_{2} \mathrm{H}_{4}$ .

Two reactions of cyclohexene are shown.

Figure for Question 19 — Edexcel A-Level Chemistry AS

Cyclohexanol is the product of Reaction 2.

Bond angle $\mathrm{a}=109.5^{\circ}$
Explain why bond angle b is smaller than bond angle a.
Include the expected value for bond angle b in your answer.
(3)

An explanation that makes reference to the following points: - (angle b is) $104.5^{\circ}$ (1) - four bond pairs (of electrons around C ) for angle a and two bond pairs and two lone pairs (of electrons around O ) for angle b (1) - lone pairs (of electrons) repel more than bond pairs (1) Mark all points independently Allow $103^{\circ}$ to $106^{\circ}$ Allow four pairs of electrons (around the central atom) for both angles Ignore covalent bond for bond pair Ignore just two lone pairs for angle b and no lone pairs for angle a Allow each lone pair reduces the bond angle by $2.5^{\circ}$ Allow lone pair-lone pair / lone pair- bond pair repulsion greater than bond pair-bond pair repulsion Allow just lone pairs repel more / lone pair repulsion greatest Ignore (electron) pairs repel to maximum separation / minimum repulsion Do not award (electron) pairs repel to minimum separation / maximum

[Maximum number: 3]

This question is about the element calcium and some of its compounds.

Calcium reacts with chlorine to form calcium chloride.

\mathrm{Ca}(\mathrm{~s})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow \mathrm{CaCl}_{2}(\mathrm{~s})

Complete the table to indicate the type(s) of bonding and structure in the species involved in this reaction.

Table for Question 20 — Edexcel A-Level Chemistry AS

Complete table: $\ce{Ca(s)}$ has metallic bonding and a giant/lattice structure; $\ce{Cl2(g)}$ has covalent bonding and a simple molecular structure; $\ce{CaCl2(s)}$ has ionic bonding and a giant ionic structure. Award 1 mark for any two or three correct scores, 2 marks for any four or five, and 3 marks for all six.

[Maximum number: 1]

This question is about the bonding in the elements of Period 3 in the Periodic Table. The melting temperatures of the Period 3 elements are shown in the table.

Table for Question 21 — Edexcel A-Level Chemistry AS

Sodium, magnesium and aluminium are metals.

State what is meant by metallic bonding.

[Maximum number: 3]

This question is about the bonding in the elements of Period 3 in the Periodic Table. The melting temperatures of the Period 3 elements are shown in the table.

Table for Question 22 — Edexcel A-Level Chemistry AS

Sodium, magnesium and aluminium are metals.

Melting temperature depends on the strength of metallic bonding.

Explain why the metallic bonding in magnesium is much stronger than that in sodium.

All question bank results loaded

Covered syllabus points

Question 1

Question (a)

Question (i)

Question (ii)

Question (b)

Question 2

Question (a)

Question (b)

Question (i)

Question (ii)

Question (iii)

Question 3

Question (a)

Question (b)

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18

Question 19

Question 20

Question 21

Question 22