# Sodium chloride and hydrogen chloride both contain chlorine. Explain why sodium chloride is an ionic compound whilst hydrogen chloride is a covalent compound, referring to the type of atoms involved and the bonding that forms in each case.

> Edexcel A-Level Chemistry (9CH0) — Topic 1 Foundations in chemistry · Explain · 5 marks

> Sodium chloride (NaCl) is a solid at room temperature that conducts electricity when dissolved in water. Hydrogen chloride (HCl) is a gas at room temperature that does not conduct electricity in its pure liquid form.

## Mark scheme (5 marks)

1. Sodium is a metal and chlorine is a non-metal (in sodium chloride)
2. In sodium chloride, electrons are transferred from sodium to chlorine, forming ions
3. The oppositely charged ions are held together by electrostatic attraction (ionic bond)
4. In hydrogen chloride, both hydrogen and chlorine are non-metals
5. In hydrogen chloride, electrons are shared between the two atoms, forming a covalent bond

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