These eight original questions cover SPM Chemistry chemical bonding. They ramp from electron arrangements to a full property explanation.
Write each answer on paper before opening the answer. The proton numbers you need are given in each question.
Practice questions
Question 1. Sodium has proton number 11. Write the electron arrangement of a sodium atom and of a sodium ion.
Answer
Atom: 2.8.1. The atom loses its one outer electron, so the ion is 2.8 with a charge of +1, written Na⁺.
Question 2. Calcium (proton number 20) and chlorine (proton number 17) react. State the ions formed and the formula of the compound.
Answer
Calcium is 2.8.8.2, so it loses 2 electrons to form Ca²⁺. Chlorine is 2.8.7, so each atom gains 1 electron to form Cl⁻.
Two chloride ions are needed to balance one calcium ion, so the formula is CaCl₂.
Question 3. Which of these is ionic: potassium bromide, hydrogen chloride, or carbon dioxide? Give a reason.
Answer
Potassium bromide is ionic, because it is formed from a metal and a non-metal, and the metal transfers electrons. Hydrogen chloride and carbon dioxide are made of non-metals only, so their atoms share electrons.
Question 4. Aluminium (proton number 13) reacts with oxygen (proton number 8). State the ions and the formula.
Answer
Aluminium is 2.8.3, so it forms Al³⁺. Oxygen is 2.6, so it forms O²⁻.
The smallest equal totals of charge are 6 positive and 6 negative, which needs 2 Al³⁺ and 3 O²⁻. The formula is Al₂O₃.
Question 5. Explain why solid sodium chloride does not conduct electricity but molten sodium chloride does.
Answer
Sodium chloride is made of Na⁺ and Cl⁻ ions. In the solid, the ions are held in fixed positions by strong electrostatic forces, so no charged particle can move.
When molten, the ions are free to move, so they carry charge and the liquid conducts.
Question 6. Substance S melts at −7 °C and does not conduct electricity in any state. State the type of particle and explain the melting point.
Answer
S is made of simple molecules. The forces between molecules are weak, so little heat energy is needed to separate them, which gives a low melting point.
It does not conduct because it has no ions or free electrons to carry charge.
Question 7. A student writes: “Covalent compounds melt easily because their covalent bonds are weak.” Correct this statement.
Answer
The covalent bonds inside each molecule are strong and do not break on melting. Only the weak forces between molecules are overcome, and that is why the melting point is low.
Question 8. Sugar solution does not conduct electricity, but potassium chloride solution does. Explain the difference.
Answer
Potassium chloride is ionic, so in solution its K⁺ and Cl⁻ ions are free to move and carry charge. Sugar is a molecular substance that dissolves as neutral molecules, so the solution has no charged particles to conduct.
If you got these wrong
Match each question to the lesson that repairs it.
- Questions 1 to 4: drawing ionic bonding representations, with electron arrangement and periodic position for question 1.
- Questions 5 to 8: explaining properties from bonding and structure.
- Question 7 in particular: distinguishing intermolecular forces from chemical bonds.
Log each mistake in the mistake log and paper-error review, then use the timed practice session builder to retry under time.
For a teacher to go through a full set with you, see online one-to-one Chemistry tuition.