JPJC 2026 Chemical Bonding Tutorial

2026 JPJC JC1 H2 Chemistry (9476) 1 Topic 3: Chemical Bonding JURONG PIONEER JUNIOR COLLEGE 2026 JC1 H2 Chemistry (9476) Tutorial 3: Chemical Bonding Level 1 – Self–Check Questions 1 A ‘dot-and-cross’ diagram of a CO molecule is shown below. Only electrons from outer shells are represented. (a) In the table below, there are three copies of this structure. On the structures, draw a circle round a pair of electrons that is associated with each of the following. (i) a dative covalent bond (ii) a covalent bond (iii) a lone pair (b) (i) State the number of  bonds and  bonds present in a CO molecule. (ii) Briefly describe the terms in italics in (b)(i). 2 Draw dot-and-cross diagrams for the following species: (a) CO2 (b) BCl3 (c) SO2 (d) H3O+ (e) SeF4 and use the VSEPR theory to predict their shapes. Suggest a value for the bond angle in (a) to (d). 3 Molecules of NH3, H2O and HF contain covalent bonds. The bonds in these molecules are polar. (a) (i) Explain what is meant by the term electronegativity. (ii) Explain why the H−F bond is polar. (iii) State and explain which of the molecules NH3, H2O or HF contains the least polar bond. (b) The boiling points of NH 3, H2O and HF are all unexpectedly high for molecules of their sizes. This is due to the type of intermolecular forces present between these molecules. (i) Identify the type of intermolecular forces present. State the conditions required for this type of intermolecular forces to be present. (ii) Draw a labelled diagram to show the type of intermolecular forces which exists between two NH3 molecules. (c) A NH3 molecule reacts with a H+ ion to form a NH4+ ion. (i) What type of bond is formed between NH3 and H+? (ii) State the conditions for this type of bonds to form. (iii) Draw a diagram to show the bonding in NH4+. (iv) By considering the number and types of electron pairs around the central atom, explain why the bond angle in NH3 is different from that in NH4+.

2026 JPJC JC1 H2 Chemistry (9476) 2 Topic 3: Chemical Bonding 4 The structures of the following substances can be simple or giant, and their bonding can be covalent, ionic or metallic. Use these terms to describe the structure and bonding in each of the following substances. Letters used to describe the substances do not represent the atomic symbols of elements. Substance Melting pt / oC Electrical Conductivity Structure and bonding (a) P −23 Non-conductor (b) Q 800 Conducts in molten and aqueous states (c) R 840 Conducts in molten and solid states (d) S 1600 Non-conductor (e) T 300 Non-conductor 5 Copper and iodine are both shiny crystalline solids. They have the same face-centered cubic crystal structures. The diagram shows the arrangement of the particles in this type of crystal lattice. In the diagram above, the particles present are represented by . Complete the table below about the type of particles and their interactions within the crystals. Solid type of particles interactions within the crystals copper crystals iodine crystals

2026 JPJC JC1 H2 Chemistry (9476) 3 Topic 3: Chemical Bonding 6 At room temperature, both sodium and sodium chloride are crystalline solids which contain ions. (a) Describe the structure and bonding in sodium with the aid of a labelled diagram. (b) Describe the bonding present in sodium chloride. (c) Compare the electrical conductivity of sodium with that of sodium chloride in their solid states. Explain your answer. (d) Explain why sodium is malleable (can be hammered into shape) while solid sodium chloride is brittle. 7 (a) Both graphite and diamond are allotropes of carbon. Graphite is a conductor of electricity but diamond is not. Explain this difference. (b) The diagram on the right shows the structure of boron nitride, which is similar to that of graphite. Explain why boron nitride is commonly used as lubricants. Key • boron  nitrogen

2026 JPJC JC1 H2 Chemistry (9476) 4 Topic 3: Chemical Bonding Level 2 – Application Questions 8 CIE Paper [9701/N07/2/2(e)] (modified) + [A-Level 2020 P2 Q2(a)] (a) Aluminium objects have a thin insoluble oxide layer on their surfaces. Explain why Al2O3 is insoluble in water. [1] The melting points of aluminium fluoride, aluminium chloride and aluminium oxide are given below. Compound Melting Point/ oC Aluminium fluoride 1291 Aluminium chloride 178 Aluminium oxide 2072 (b) (i) Draw the dot-and-cross diagram of Al2O3. [1] (ii) Suggest explanations for the difference in melting points between A lF3 and Al2O3. [2] (c) Suggest explanations for the differences in melting points between A l2O3 and AlCl3. [2] (d) When solid aluminium chloride is heated above 451 K, a vapour is formed which has Mr = 267. When this vapour is heated above 1100 K, the vapour has Mr = 133.5. (i) What are the molecular formulae of these two forms of aluminium chloride at 460 K and at 1150 K respectively? [2] (ii) Draw a ‘dot -and-cross’ diagram of the form of aluminium chloride that exists at the higher temperature. [1] (iii) Use your knowledge of VSEPR theory to name the shapes of and state the bond angles for the compound you drew in (ii). Explain your reasoning. [2] (iv) Draw a diagram of the form of aluminium chloride that exists at the lower temperature. Illustrate clearly the different types of bonds present. [1] (e) Aluminium is a silvery -white, lightweight metal. Aluminium is used in a huge variety of products including cans, foils, kitchen utensils, window frames. Explain why the melting point and electrical conductivity of sodium is lower than that of aluminium. [2]

2026 JPJC JC1 H2 Chemistry (9476) 5 Topic 3: Chemical Bonding 9 For each of the following substances, (a) F2O (b) ClF3 (c) IF5 (d) NO2– (e) PCl4+ (f) PCl6– (i) draw ‘dot-and-cross’ diagram showing the electrons (outer shells only). [5] (ii) draw the structure and use the VSEPR (valence shell electron pair repulsion theory) to suggest its shape. [10] (a) F2O (b) ClF3 (c) IF5 Dot-and cross diagram Shape (d) NO2– (e) PCl4+ (f) PCl6– Dot-and cross diagram Shape

2026 JPJC JC1 H2 Chemistry (9476) 6 Topic 3: Chemical Bonding 10 [N2019 P3 Q1(a)(b)] BF3, H2O, and NH 3 are three compounds whose central atoms in their molecules are elements in period 2 of the Periodic Table. (a) Use the VSEPR theory to state and explain the bond angles in the molecules of these three compounds. [4] (b) Draw the three molecules BF3, H2O, and NH3. For each molecule, indicate clearly the polarity of each of the bonds it contains, and its overall net polarity. [4] 11 [N10 P3 Q4(c)] (a) Draw dot-and-cross diagrams to show the bonding in the molecules of NO 2 and O3. Each molecule contains a dative covalent bond. In each case you should distinguish carefully between electrons originating from the central atom and those from the two outermost atoms. Include all lone pairs in your diagrams. [2] (b) Suggest a value for the bond angle in each of the above two molecules, giving reasons for your choice. [2] (c) The compound FO2 does not exist, but ClO2 does. By considering the possible types of bonding in the two compounds, suggest reasons for this difference. (Assume that the halogen atom occupies a central position in each of these molecules.) [2] (d) [2022 P3 Q4(d)(i)] Dinitrogen trioxide, N2O3, is formed when nitrogen monoxide and nitrogen dioxide are mixed at low temperature. N2O3 is readily hydrolysed to nitrous acid, HNO2. N2O3 contains a N—N bond. Draw the dot-and-cross di