Contents

States of matter

Atoms, elements and compounds

Stoichiometry

Electrochemistry

ElectrolysisBeing prepared
Electrolysis of solutions and electroplatingBeing prepared
Fuel cellsBeing prepared

Chemical energetics

Chemical reactions

Acids, bases and salts

Acids, bases and indicators
OxidesBeing prepared
Making saltsBeing prepared

The Periodic Table

Reading the tableBeing prepared
Group I: the alkali metalsBeing prepared
Group VII: the halogensBeing prepared
Transition elements and noble gasesBeing prepared

Metals

Metals and alloysBeing prepared
The reactivity seriesBeing prepared
CorrosionBeing prepared
Extracting metalsBeing prepared

Chemistry of the environment

WaterBeing prepared
FertilisersBeing prepared
Air quality and climateBeing prepared

Organic chemistry

Naming organic moleculesBeing prepared
Crude oil and alkanesBeing prepared
AlkenesBeing prepared
Alcohols and carboxylic acidsBeing prepared
PolymersBeing prepared

Experimental techniques and chemical analysis

Mixtures and separation
Measuring and planning experimentsBeing prepared
Crystallisation
Distillation
Paper chromatography
Choosing methods and checking purityBeing prepared
TitrationBeing prepared
Gas testsBeing prepared
Anion testsBeing prepared
Cation and flame testsBeing prepared

Part 2 of 2

Page 02

Dots and crosses

identify

Try it yourself

The diagram shows potassium chloride, outer shells only. One atom’s electrons are drawn as dots and the other atom’s as crosses. Which statement about the crosses is correct?

identify: name or select.

Dot-and-cross diagram of potassium chloride, outer shells only. A potassium ion in square brackets with charge +, its outer shell 8 crosses. A chloride ion in square brackets with charge −, its outer shell 7 dots and 1 cross.

Choose one answera.They are protons, and they give the potassium ion its positive chargeb.They are shared by both ions, and they hold the two ions togetherc.They were chlorine’s electrons, and one of them has moved to potassiumd.They were potassium’s electrons, and one of them has moved to chlorine

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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