Sodium chloride is an ionic compound formed when sodium reacts with chlorine. Explain how an ionic bond forms between a sodium atom and a chlorine atom, and describe the structure of the ionic compound that results.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Sodium is a metal in Group 1 of the periodic table. Chlorine is a non-metal in Group 7 of the periodic table. When sodium reacts with chlorine, sodium chloride is formed.
Model answer (5 marks)
Sodium loses one electron to form a Na⁺ ion.
Chlorine gains that electron to form a Cl⁻ ion.
The oppositely charged Na⁺ and Cl⁻ ions attract each other, forming an ionic bond.
The ionic bond is a strong electrostatic attraction between the ions.
The resulting NaCl is a giant lattice structure, with many Na⁺ and Cl⁻ ions arranged in a regular pattern.
Chlorine gains that electron to form a Cl⁻ ion.
The oppositely charged Na⁺ and Cl⁻ ions attract each other, forming an ionic bond.
The ionic bond is a strong electrostatic attraction between the ions.
The resulting NaCl is a giant lattice structure, with many Na⁺ and Cl⁻ ions arranged in a regular pattern.
Examiner tips
- Use the exact terms: ‘loses one electron’, ‘gains that electron’, ‘Na⁺’, ‘Cl⁻’, ‘ionic bond’, ‘electrostatic attraction’, ‘giant lattice’.
- Show the sequence of electron transfer and the resulting attraction.
- Mention the regular arrangement of ions in the lattice.
- Keep the answer concise and to the point.
Common mistakes
- Confusing covalent with ionic bonding, e.g. saying electrons are shared rather than transferred.
- Using vague phrases like ‘strong bond’ without specifying electrostatic attraction.
- Omitting the lattice structure or describing it incorrectly as a molecule rather than a crystal lattice.
Mark scheme (5 marks)
- Sodium loses one electron (to form a positively charged ion / Na⁺)
- Chlorine gains that electron (to form a negatively charged ion / Cl⁻)
- An ionic bond is formed between the oppositely charged ions (Na⁺ and Cl⁻)
- The ionic compound is held together by strong electrostatic forces (of attraction between oppositely charged ions)
- Sodium chloride exists as a giant ionic structure / lattice (with many ions arranged in a regular pattern)
Key terms in this question
ionic bond · ion · ionic compound
Related
- All OCR A-Level Chemistry B: Salters (H433) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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