Iron and copper are both transition metals. Explain why iron is described as a transition metal and describe two ways in which the physical properties of iron differ from those of potassium, a Group 1 metal.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
Iron is a transition metal because it is a d‑block element with a partially filled d‑sub‑shell – its electron configuration ends in 3d⁶4s², giving unfilled 3d orbitals.
Compared with potassium:
1. Iron has a much higher melting point (1538 °C vs 63.5 °C).
2. Iron is harder and stronger, and less malleable than potassium.
3. Iron has a higher density (7.87 g cm⁻³ vs 0.86 g cm⁻³).
4. Iron is a better conductor of electricity (and heat) than potassium.
Compared with potassium:
1. Iron has a much higher melting point (1538 °C vs 63.5 °C).
2. Iron is harder and stronger, and less malleable than potassium.
3. Iron has a higher density (7.87 g cm⁻³ vs 0.86 g cm⁻³).
4. Iron is a better conductor of electricity (and heat) than potassium.
Examiner tips
- State the d‑block/partially filled d‑sub‑shell for iron first. Use specific numerical values for melting point and density. Mention hardness/malleability as a clear physical difference. Show conductivity as a contrasting property.
Common mistakes
- Confusing potassium’s properties with iron’s (e.g. saying potassium has a higher melting point). Omitting the d‑sub‑shell explanation for iron. Using vague terms like "more reactive" instead of specific physical properties.
Mark scheme (5 marks)
- Transition metals have an incomplete d sub-shell (or d-block element with partially filled d orbitals) — accept: iron has electrons in d orbitals / iron is a d-block element
- Iron has a higher melting point than potassium
- Iron is harder / stronger / less malleable in comparison to potassium
- Iron has a higher density than potassium
- Iron has a higher electrical conductivity than potassium OR iron is a better conductor of electricity/heat — accept any valid comparison of a physical property not already credited
Key terms in this question
Related
- All AQA A-Level Chemistry (7405) revision notes →
- How to answer a "Explain and Describe" question →
- Decode the mark scheme abbreviations →
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