Calcium chloride has the formula CaCl₂. Hydrogen chloride has the formula HCl. Explain the difference between a compound and an element, and state whether calcium chloride and hydrogen chloride are the same type of compound. Give a reason for your answer.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Calcium is a metal in Group 2 of the periodic table. Chlorine is a non-metal in Group 7. Hydrogen chloride is a gas at room temperature.
Model answer (4 marks)
A compound is a substance made up of two or more different types of atoms chemically combined together.
Both calcium chloride (CaCl₂) and hydrogen chloride (HCl) are compounds, not elements.
Each contains two different elements chemically combined.
Calcium chloride is an ionic compound (metal–non‑metal, ionic bond) while hydrogen chloride is a covalent compound (non‑metal–non‑metal, covalent bond), so they are different types of compound.
Both calcium chloride (CaCl₂) and hydrogen chloride (HCl) are compounds, not elements.
Each contains two different elements chemically combined.
Calcium chloride is an ionic compound (metal–non‑metal, ionic bond) while hydrogen chloride is a covalent compound (non‑metal–non‑metal, covalent bond), so they are different types of compound.
Examiner tips
- Define compound clearly; mention two different elements. State both are compounds. Explain ionic vs covalent nature to show difference. Use correct terminology (ionic, covalent, metal, non‑metal).
Common mistakes
- Confusing elements with compounds; writing that one is an element. Failing to mention both are compounds. Not specifying ionic vs covalent nature.
Mark scheme (4 marks)
- A compound is a substance made up of two or more types of atoms chemically combined together
- Both calcium chloride and hydrogen chloride are compounds (not elements)
- Both substances contain more than one type of atom chemically combined / both contain two different elements
- Calcium chloride is an ionic compound (formed between a metal and a non-metal / contains an ionic bond) whereas hydrogen chloride is a covalent compound (formed between two non-metals / contains a covalent bond), so they are different types of compound
Key terms in this question
Related
- All Pearson Edexcel International GCSE Chemistry (4CH1) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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