2.4

Structure and properties

Cambridge IGCSE Chemistry (0620)  · Unit 2: Atoms, elements and compounds  · 9 flashcards

Structure and properties is topic 2.4 in the Cambridge IGCSE Chemistry (0620) syllabus , positioned in Unit 2 — Atoms, elements and compounds , alongside Elements, compounds and mixtures, Atomic structure and Bonding.  In one line: Positive ions are called cations. They are formed when an atom loses electrons.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical).

The deck below contains 9 flashcards — 3 definitions and 1 key concept — covering the precise wording mark schemes reward.  Use the 3 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

Positive ions called, and how are they formed

Positive ions are called cations. They are formed when an atom loses electrons.

Example: sodium (Na) loses one electron to form a sodium ion (Na+).

What the Cambridge 0620 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Describe Describe the formation of positive ions, known as cations, and negative ions, known as anions
  2. State State that an ionic bond is a strong electrostatic attraction between oppositely charged ions
  3. Describe Describe the formation of ionic bonds between elements from Group I and Group VII, including the use of dot-and-cross diagrams
  4. Describe Describe the properties of ionic compounds: (a) high melting points and boiling points (b) good electrical conductivity when aqueous or molten and poor when solid
  5. Describe Describe the giant lattice structure of ionic compounds as a regular arrangement of alternating positive and negative ions Supplement
  6. Describe Describe the formation of ionic bonds between ions of metallic and non-metallic elements, including the use of dot-and-cross diagrams Supplement
  7. Explain Explain in terms of structure and bonding the properties of ionic compounds: (a) high melting points and boiling points (b) good electrical conductivity when aqueous or molten and poor when solid Supplement
Definition Flip

What are positive ions called, and how are they formed?

Answer Flip

Positive ions are called cations. They are formed when an atom loses electrons.

Example: sodium (Na) loses one electron to form a sodium ion (Na+).
Definition Flip

What are negative ions called, and how are they formed?

Answer Flip

Negative ions are called anions. They are formed when an atom gains electrons.

Example: chlorine (Cl) gains one electron to form a chloride ion (Cl-).
Definition Flip

Define an ionic bond.

Answer Flip

An ionic bond is a strong electrostatic attraction between oppositely charged ions. This attraction holds the ions together in a lattice structure.

Example: Na+ and Cl- attract to form NaCl.
Key Concept Flip

Describe the arrangement of ions in an ionic compound's structure.

Answer Flip

Ionic compounds have a giant lattice structure, which is a regular arrangement of alternating positive and negative ions. This structure extends in three dimensions.

Example: NaCl has alternating Na+ and Cl- ions.
Key Concept Flip

Explain why ionic compounds have high melting and boiling points.

Answer Flip

Ionic compounds have high melting and boiling points due to the strong electrostatic forces of attraction between oppositely charged ions. A large amount of energy is needed to overcome these strong forces.

Example: NaCl has a melting point of 801°C.
Key Concept Flip

Explain the electrical conductivity of ionic compounds when solid vs. aqueous or molten.

Answer Flip

Ionic compounds conduct electricity when aqueous or molten because the ions are free to move and carry charge. When solid, the ions are fixed in the lattice and cannot move, so they do not conduct.

Example: Solid NaCl doesn't conduct, but molten NaCl does.
Key Concept Flip

Give an example of an ionic compound formed between a Group I and a Group VII element.

Answer Flip

Sodium chloride (NaCl) is formed between sodium (Group I) and chlorine (Group VII). Sodium loses an electron to form Na+, and chlorine gains an electron to form Cl-. They then attract each other.

Key Concept Flip

Give an example of an ionic compound formed between a metal and a non-metal element.

Answer Flip

Magnesium oxide (MgO) is formed between magnesium (metal) and oxygen (non-metal). Magnesium loses two electrons to form Mg2+, and oxygen gains two electrons to form O2-. They then attract each other.

Key Concept Flip

What type of elements are most likely to create ionic bonds?

Answer Flip

Elements with a large difference in electronegativity are most likely to form ionic bonds. This typically occurs between metals (low electronegativity) and nonmetals (high electronegativity).

Example: Sodium (0.93) and Chlorine (3.16).

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2.3 Bonding 3.1 Formulae

Key Questions: Structure and properties

What are positive ions called, and how are they formed?

Positive ions are called cations. They are formed when an atom loses electrons.

Example: sodium (Na) loses one electron to form a sodium ion (Na+).
What are negative ions called, and how are they formed?

Negative ions are called anions. They are formed when an atom gains electrons.

Example: chlorine (Cl) gains one electron to form a chloride ion (Cl-).
Define an ionic bond.

An ionic bond is a strong electrostatic attraction between oppositely charged ions. This attraction holds the ions together in a lattice structure.

Example: Na+ and Cl- attract to form NaCl.

More topics in Unit 2 — Atoms, elements and compounds

Structure and properties sits alongside these Chemistry decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

2.1 Elements, compounds and mixtures

11 flashcards
2.2 Atomic structure

12 flashcards
2.3 Bonding

1 flashcards

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0620 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

properties melting point boiling point conductivity electrical conductivity solubility hardness brittleness malleable ductile giant ionic giant covalent simple molecular metallic structure

Key terms covered in this Structure and properties deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

Positive ions called, and how are they formed
Negative ions called, and how are they formed
An ionic bond

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How to study this Structure and properties deck

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