Ten original SPM-style multiple-choice questions and three structured questions with full model answers for the Chemical Bond chapter, testing octet reasoning, ionic and covalent dot-and-cross work, dative and hydrogen bonds, and explaining properties from bonding.
These questions are original, written in SPM style on the Chemical Bond content standards, Paper 1 is an objective (multiple-choice) paper. Try each one before checking the answer. Cover the working, attempt it, then mark yourself against the reasoning given.
Part A, Multiple-choice questions
1. Why do most atoms form chemical bonds?
- A. To become heavier
- B. To achieve a stable electron arrangement like a noble gas
- C. To lose their protons
- D. To become metals
Answer: B. Atoms bond to reach a full outer shell, the stable arrangement of the nearest noble gas.
2. Which element exists as single atoms and does not normally form bonds?
- A. Sodium
- B. Chlorine
- C. Argon
- D. Oxygen
Answer: C. Argon is a Group 18 noble gas with a full outer shell, so it is already stable.
3. An ionic bond is best described as the force between ions formed by
- A. sharing electrons
- B. transfer of electrons
- C. sharing protons
- D. transfer of neutrons
Answer: B. Ionic bonding forms when electrons are transferred from a metal to a non-metal.
4. Calcium has electron arrangement 2.8.8.2 and chlorine 2.8.7. The formula of calcium chloride is
- A. CaCl
- B. CaCl₂
- C. Ca₂Cl
- D. Ca₂Cl₃
Answer: B. Ca loses 2 electrons to form Ca²⁺; each Cl gains 1, so two Cl⁻ are needed, CaCl₂.
5. When a metal atom forms an ionic bond, it
- A. gains electrons and becomes negative
- B. loses electrons and becomes positive
- C. shares electrons and stays neutral
- D. gains protons and becomes positive
Answer: B. A metal loses its outer electrons to become a positively charged cation.
6. How many pairs of electrons are shared in a nitrogen molecule, N₂?
- A. 1
- B. 2
- C. 3
- D. 4
Answer: C. Nitrogen forms a triple bond, so three pairs of electrons are shared.
7. Which molecule contains a double covalent bond?
- A. H₂
- B. HCl
- C. O₂
- D. CH₄
Answer: C. Oxygen atoms share two pairs of electrons, forming a double bond (O=O).
8. In the ammonium ion, NH₄⁺, the dative bond forms because
- A. the H⁺ ion donates two electrons
- B. nitrogen donates both electrons of the shared pair
- C. each atom donates one electron
- D. electrons are transferred completely
Answer: B. The lone pair on nitrogen supplies both electrons, so it is a dative (coordinate) bond.
9. Which substance conducts electricity when molten but not when solid?
- A. Sugar (a molecular solid)
- B. Sodium chloride (an ionic solid)
- C. Iodine (a molecular solid)
- D. Paraffin wax
Answer: B. In an ionic solid the ions are fixed; when molten they are free to move and carry charge.
10. Simple covalent compounds usually have low melting points because
- A. their covalent bonds are weak
- B. the forces between molecules are weak
- C. they contain free ions
- D. they contain free electrons
Answer: B. Only the weak forces between molecules are overcome on melting; the covalent bonds stay intact.
11. Which pair of substances would you expect to dissolve in water rather than in an organic solvent?
- A. Iodine and naphthalene
- B. Sodium chloride and potassium bromide
- C. Wax and petrol
- D. Sulfur and iodine
Answer: B. Sodium chloride and potassium bromide are ionic, and ionic compounds generally dissolve in water.
12. Which atom reaches a stable arrangement with only two outer electrons (a duplet) rather than an octet?
- A. Sodium
- B. Carbon
- C. Hydrogen
- D. Chlorine
Answer: C. Hydrogen is stable with two electrons, matching helium, not with an octet.
13. A compound is a poor conductor as a solid, conducts when molten, and has a high melting point. It is most likely
- A. a metal
- B. a simple covalent compound
- C. an ionic compound
- D. a noble gas
Answer: C. High melting point plus conduction only when molten are the signatures of an ionic compound.
Part B, Structured questions
Question 1. Sodium (2.8.1) reacts with oxygen (2.6) to form sodium oxide.
- (a) State the type of bond formed. (Ionic bond.)
- (b) Describe, in terms of electron transfer, how the compound forms. (Each sodium atom transfers its one outer electron; two sodium atoms are needed to supply the two electrons that one oxygen atom gains. Sodium becomes Na⁺ (2.8) and oxygen becomes O²⁻ (2.8). The oppositely charged ions are held by strong electrostatic forces of attraction.)
- (c) Write the formula of sodium oxide. (Na₂O, two Na⁺ balance one O²⁻.)
Question 2. Ammonia has the formula NH₃. Nitrogen is 2.5 and hydrogen has one electron.
- (a) State the type of bond between nitrogen and hydrogen. (Covalent bond.)
- (b) How many bonding pairs and lone pairs does the nitrogen atom have? (Three bonding pairs and one lone pair.)
- (c) Explain how ammonia can form the ammonium ion, NH₄⁺. (The nitrogen lone pair forms a dative bond with a hydrogen ion H⁺, which has no electrons; nitrogen supplies both electrons of that bond.)
- (d) Ammonia is very soluble in water. State the type of intermolecular attraction responsible. (Hydrogen bonding between ammonia and water molecules.)
Question 3. The table compares magnesium chloride (ionic) and tetrachloromethane, CCl₄ (simple covalent).
- (a) Which compound has the higher melting point, and why? (Magnesium chloride, because its giant ionic lattice is held by strong electrostatic forces between oppositely charged ions that need a large amount of energy to overcome; CCl₄ has only weak forces between molecules.)
- (b) Which compound conducts electricity when molten? Explain. (Magnesium chloride, because when molten its ions are free to move and carry charge; CCl₄ has no ions.)
- (c) State which compound is more soluble in water and which in an organic solvent. (Magnesium chloride is more soluble in water; CCl₄ is more soluble in an organic solvent, “like dissolves like”.)
Question 4. Methane, CH₄, and water, H₂O, are both simple covalent molecules. Carbon is 2.4, oxygen is 2.6 and hydrogen has one electron.
- (a) State how many single covalent bonds there are in a methane molecule. (Four, carbon shares one electron with each of four hydrogen atoms to complete its octet.)
- (b) State the number of lone pairs on the oxygen atom in water. (Two lone pairs.)
- (c) Explain why the boiling point of water is much higher than that of methane. (Water molecules form hydrogen bonds with one another because hydrogen is bonded to the very electronegative oxygen; these extra attractions between molecules need more energy to overcome. Methane cannot form hydrogen bonds, so its molecules are held only by weaker forces and it boils at a much lower temperature.)
- (d) State why neither methane nor pure water is a good conductor of electricity. (Simple covalent molecules have no free-moving ions or electrons to carry charge.)
Marking yourself
Give yourself the mark only when the reason is present, not just the answer, in this chapter the reason is where the marks are. If you missed the “strong electrostatic forces” or “free to move” phrases, note them and try similar questions again. A one-to-one teacher can mark your structured answers and dot-and-cross diagrams the way an examiner would across the SPM Chemistry papers, so you learn exactly where a part-mark becomes full marks.
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