Contents
Independent final check
Explain without the key
identify / explain / determine / describe / state
Final check
The table gives data for three solids, P, Q and R. One of them is an ionic compound. (a) Identify the ionic compound, and explain why R is not ionic although it conducts when molten. (b) The ionic compound is made of ions with 12 protons and 10 electrons, and ions with 35 protons and 36 electrons. Determine the charge on each ion, and describe how each ion forms from its atom. (c) Describe the structure of the ionic compound, and state what holds its ions together. (d) Supplement: explain, in terms of structure and bonding, its high melting point and its three conductivity results.
identify: name or select. explain: give reasons and connect them to evidence. determine: find the answer from the information given. describe: give the features or what happens. state: give a concise answer.
| Solid | Melting point (°C) | Conducts as a solid? | Conducts when molten? | Conducts when dissolved in water? |
|---|---|---|---|---|
| P | 711 | no | yes | yes |
| Q | 146 | no | no | no |
| R | 420 | yes | yes | does not dissolve |
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Scope and sources
Cambridge IGCSE Chemistry 0620 · 2026–2028 v2 · Original learning materials.
Ions and ionic bonds (2.4 Core 1–4, Supplement 5–7): cations and anions, the ionic bond as a strong electrostatic attraction between oppositely charged ions, dot-and-cross diagrams for Group I with Group VII compounds and, in the Supplement, for other metallic and non-metallic elements, the high melting and boiling points of ionic compounds and their conduction when molten or aqueous but not when solid, the giant lattice of alternating ions, and how that structure explains the properties. Covalent bonds, giant covalent and metallic structures, writing formulae and naming compounds in general, and electrolysis are left to other modules.
Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.
Official Cambridge syllabus